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    GLUFOSINATE AMMONIUM

    First draft prepared by Dr. Otto Meyer,
    National Food Agency,
    Soborg, Denmark

    Ammonium 4-[hydroxy(methyl)phosphinoyl]-DL-homoalaninate.

    EXPLANATION

         Glufosinate ammonium is the active ingredient in a new
    non-selective herbicide. The herbicidal action of this substance, a
    phosphinic acid analogue of glutamic acid, is related to the
    inhibition of glutamine synthetase, an enzyme utilized in ammonia
    detoxification and amino acid metabolism in plants.  Glufosinate
    ammonium has not previously been evaluated by JMPR.


    BIOLOGICAL DATA

    Biochemical aspects

    Absorption, distribution and excretion

         Glufosinate ammonium, 14C (3,4-14C, 2-2.12 mCi/g) was
    administered orally in a single dose of 30 mg/kg bw to 5 male and 5
    female SPF Wistar rats, 10-12 weeks of age (1 male and 1 female served
    as controls).  Excretion was 84% in faeces and 7% and 12% in urine for
    males and females, respectively, after 0-168 hours. More than 92% in
    both sexes was excreted within 24 hours.  The biological half-lives
    for the biphasic excretion were 5-7 hours for phase 1 in urine and
    faeces and 1.5 days for phase 2.  After 7 days only the kidneys,
    testes, and liver in males and the kidneys and liver in females
    contained regularly detectable concentrations, none exceeding 0.4 ppm. 
    Concentrations found in other tissues (spleen, bone, brain) were 0.2
    ppm and below.  The total balance of tissue residues and excreted
    radioactivity was 95% for males and 96% for females (Kellner & Eckert,
    1985).

         A single dose at about 2 mg/kg bw, 14C-labelled at the
    2-position (19.4 mCi/g) was administered intravenously and orally to
    groups of 10 male and 10 female SPF Wistar rats, weighing about 200 g. 
    The blood levels after oral administration were low and only
    measurable in males up to 3 hours (C max. 0.008 µg/ml) and in females
    up to 8 hours (C max 0.029 µg/ml) after application.  After iv
    application the concentrations in blood could be followed for up to 2
    days after application, the t´ being about 20 min, 3-4 hours and
    97-126 hours.  After oral administration 89% and 81% of the substance
    was excreted in faeces in males and females, respectively, while the
    corresponding figures for renal excretion were 7% and 14%,
    respectively.  More than 97% (males) or 92% (females) of the faecally
    excreted radioactivity was eliminated after one or two days for males
    and females. The t´ for the biphasic renal elimination was: males 5
    hours and females 7 hours, respectively, and males 58 hours and
    females 52 hours.  After intravenous administration the figures for
    renal and faecal excretion were: males 85% and females 93%, and males
    18% and females 8%, respectively. The t´ for the bi-phasic renal
    elimination was 8 hours first place for both sexes and males 64 hours
    and females 52 hours second place. No detectable radioactivity was
    found in expired air over 24 hours at a limit of detection of 0.1%. 
    Of the organs/tissues examined 7 days after oral application, only the
    kidneys, testes and liver of males and liver and kidneys of females
    contained detectable concentrations, none exceeding 0.2 ppm.  These
    values are equivalent to about 0.2% or 0.1% of the dose. The rate of
    absorption was estimated to be females 13% and males 8% (Kellner &
    Eckert, 1983).

         Glufosinate ammonium was administered orally in doses of 2 mg/kg
    bw/day to 5 male and 5 female SPF Wistar rats (1 rat/sex served as
    controls), 10-12 weeks of age for 14 days. On the 15th day the animals
    received a single dose of glufosinate ammonium (3,4-14C, 21.87
    mCi/g).  A total of 91% and 89% was excreted in faeces in males and
    females, respectively, and 9% in the urine of both sexes.  More than
    90% (males) and 94% (females) of the excreted radioactivity was
    eliminated after 1 day.  The biological half-lives for the biphasic
    excretion were 5-6 hours and 1.3-2 days. After 7 days only the
    kidneys, testes, and liver in males and the kidneys, liver, and spleen
    (0.008 ppm) in females contained regularly detectable concentrations,
    all under 0.1 ppm.  The total of radioactivity found in excreta and
    tissues was males 101.4% and females 97.83% (Kellner & Eckert 1985).

         Groups of 28 male SPF Wistar rats weighing 167-198 g received one
    single dermal application of 0.1, 1.0 and 10 mg radiolabelled
    glufosinate ammonium (3, 4-14C, 47.7 mCi/g)/kg bw for a maximum of 10
    hours.  Four males served as controls.  Absorption of radioactivity
    from the skin was highest at the lowest dose level (51%, 43 and 26%
    after 168 hours for low-, mid- and high-dose, respectively). The
    excretion pattern showed that both urinary and faecal (biliary)
    excretion represent important routes for the elimination of test
    substance and/or metabolites. Total recoveries of radioactivities
    ranged, on average, for all animals between 80% and 91%.  Highest
    residual radioactivity in organs/tissues and blood were found 4-10
    hours after starting of exposure (Ellgehausen, 1986).

         Two male and 2 female beagle dogs, 4-6 months of age were
    administered a single dose of 8 mg radiolabelled glufosinate ammonium
    (3,4-14C, 54.08 mCi/g)/kg bw.  Within 24 hours, males 95% and females
    94% of the dose was excreted. The urinary excretion constituted 9-10%. 
    Blood and plasma levels reached the maximum (range 0.1-0.5 µg/g) after
    2 hours for males and 4 hours for females, and the half-life
    thereafter was 2 to 4 hours. Residual radioactivity in the different
    brain regions in males and females ranged from 0.02-0.07 µg/g after
    6-24 hours.  The values for heart, liver, and kidney ranged between
    0.02-0.06, 1.3 and 1.2-2.4 µg/g, respectively.  The only metabolite
    found was 3-methylphosphinico-propionic acid.  This metabolite
    constituted 11-16% of the residue in urine, while the parent compound
    was found to range between 84-89%. The extractable residue in faeces
    (68-93% of the radioactivity found in faeces) was exclusively the
    parent compound.  Analysis of the extractable residue in liver and
    kidney after 6-24 hours (90-99%) showed only parent compound. 
    Analysis of selected plasma samples collected 2 and 6 hours after
    administration showed that 75-84% of the radioactivity present was
    extractable and only 16-25% was precipitated with plasma proteins. 
    Only parent compound was detected (Ellgehausen, 1986).

         Groups of 6 male and 6 female Beagle dogs about 5-8 months of age
    were administered glufosinate ammonium (purity 95.3%) perorally in
    capsules in doses 0, 1 and 8 mg/kg bw/day for 18 days.  Four and one

    animals/sex/group then received radiolabelled substance in the same
    daily doses for 10 days or one day,  respectively (3,4-14C, 54.08
    mCi/g).  One animal/sex/group was sacrificed without being dosed with
    the radiolabelled substance, the one animal/sex/dose receiving one
    dose was sacrificed 6 hours after dosing and the 4 animals/sex/dose
    24, 48 and 96 hours after the last dose, respectively.  Excretion of
    the substance was almost complete for males and females of both dose
    levels ranging from males 97% to females 98% of the administered dose.
    Urinary excretion constituted 14-17% of radioactivity. Blood and
    plasma levels showed that a steady state condition between absorption
    and excretion was reached after 2-5 days.  Levels of radioactivity at
    high dose level in different parts of the brain showed relatively low
    levels, less than 0.6 µg/g in all cases.  Significantly lower
    concentrations were found in cortex, spinal cord, and heart.  After 96
    hours the figures approximated the limits of quantification.

         The maximum levels in liver and kidney of 3.7 and 6.5 µg/g,
    respectively, were reached 48 and 24 hours after the last treatment in
    top-dosed animals. The elimination of radioactivity in liver, kidneys
    and heart was shown to be rapid.  Analysis of urinary radioactivity
    and of radioactivity found in faeces, kidney and liver showed that
    besides the parent molecule only 3-methylphosphinico-propionic acid
    was present. The parent compound accounted for males 100% and females
    89% of radioactivity in urine. In liver and especially kidneys the
    metabolite generally exceeded the amount of parent compound
    (Ellgehausen, 1986).

         Two lactating Swiss mini-goats, weighing 21.5 and 20 kg received
    five oral doses of a radiolabelled equimolar mixture of glufosinate
    ammonium (3,4-14C, 23.9 mCi/g) and the major metabolite in animal,
    plant and soil, 3-methylphosphinico-propionic acid (3-14C, 24.8
    mCi/g), at a dose level of about 3.5 mg/kg bw.  A third goat served as
    control.  The total amount of radioactivity recovered 96 and 8 after
    last administration varied substantially between the two animals - 75%
    and 98% of which 37% and 48% was found in urine, 35% and 47% in
    faeces, 0.02% and 0.03% in milk and 2.5% and 0.1% in tissues/organs
    for the two goats.  Experimenters noted that the amount of
    radioactivity remaining in the gut of the 8 hour animal was not
    determined. The level in the blood reached a plateau 8 hours after
    administration of the last dose (0.2 µg/g), and after 96 hours the
    level was close to limit of quantification (0.01 µg/g). In milk the
    maximum concentration of 0.1 µg/ml was found 8 and 24 hours after the
    last administration.  Ninety-six hours after last administration the
    level was decreased to 0.03 µg/g.  Residual radioactivity in organs
    and tissues ranged from 24 µg/g (kidneys) to 0.06 µg/g (brain) in the
    animal killed 8 hours after last dose.  In the 96-hour animal, the
    residual radioactivity was 0.4 µg/g (kidneys) and 0.07 µg/g (brain). 
    On average the radioactivity residue levels 96 hours after the last
    administration were 14 times lower than after 8 hours  Four days
    later, the residual radioactivity accounted for 0.4 mcg/g (kidneys)
    and 0.07 mcg/g (brain). On average the radioactivity residue levels 96

    hours after the last administration were 14 times lower than after 8
    hours (Ellgehausen, 1984b).

         Equimolar mixtures of radiolabelled glufosinate ammonium
    (3,4-14C, 23.9 mCi/g) and its major metabolite,
    3-methylphosphinico-propionic acid (3-14C, 24.8 mCi/g), were
    administered to 10 Leghorn hybrid laying hens perorally in daily doses
    of 3.5 mg/kg bw for five days (additional 2 hens served as controls). 
    The substance and its major metabolite do not seem to accumulate or be
    retained by laying hens (Ellgehausen, 1984a).

         One single dose of 20 mg/kg bw radiolabelled
    3-methylphosphinico-propionic acid (3-14C, 6.810 mCi/g) was
    administered perorally or iv to groups of 5 female SPF Wistar rats
    weighing 175-200 g.  Four days after administration the perorally
    dosed rats excreted 92% in urine and 3.7% in faeces while iv dosed
    rats excreted 93% in urine and 0.6% in faeces.  For both applications
    the half-lives were 6-7 hours.  The findings demonstrate a nearly
    complete absorption of this metabolite (Kellner & Eckert, 1984).

    Biotransformation

         Glufosinate ammonium, (3,4-14C, 4.91 mCi/g) was administered to
    20 female SPF Wistar rats weighing an average of 200 g in a single
    oral dose of 10.8 mg/kg bw.  A total of 10.6% of the radioactivity was
    excreted in the urine and 82% in faeces within 48 h after dosing and
    in the period 49-120 h after administration of the compound 1.3% and
    1.2% of the radioactivity was eliminated via urine and faeces,
    respectively. In urine 8.5% of the applied dose was identified as the
    parent compound, 0.5% as 3-methylphosphinico-propionic acid and 1% as
    3-methylphosphinico-3-oxo-propionic acid. In faeces 74% of the applied
    dose was active ingredient, 2.6% was 3-methylphosphinico-propionic
    acid and 5.8% an unidentified metabolite (Dorn  et al., 1983).

         Glufosinate ammonium, (3.4-14C, 49.4 mCi/g) was administered to
    10 male and 10 female SPF Wistar rats, 10 weeks of age (2 rats/sex
    served as controls) in a single oral dose of 2.5 and 2.9 mg/kg bw,
    respectively.  More than 80% of the applied radioactive dose was
    eliminated via faeces and 6% via urine during the first 24 h after
    administration and the total recovery after 96 h was 99.7% and 98.1%
    for males and females respectively. The highest radioactivity in
    organs and tissues after 4 days was found in liver, 0.06% or 0.003
    mg/kg and 0.06% or 0.04 mg/kg, and in kidneys, 0.09% or 0.22 mg/kg
    and 0.02 or 0.01 mg/kg for males and females respectively. Blood,
    brain, spleen and fat contained significantly lower residues. The
    excreted radioactivity in faeces (extractable part = 86 % of the total
    excreted activity during 48 h) and in urine (during 24 hours)
    represents only the parent compound (Wink  et al., 1986).

         The metabolism of glufosinate ammonium (3,4-14C, 21.86 mCi/g)
    was investigated in 20 male and 20 female Wistar SPF rats, 10 weeks of
    age receiving a single oral dose of 29.4 mg/kg bw.  Ninety-six h after
    administration the recovery of radioactivity was 96% and 88% in
    females and males, respectively.  Females and males excreted 14 and
    17% in urine and 83 and 71% in faeces, respectively.  The main amount
    (> 86%) of radioactivity excreted via urine was found in urine
    samples taken 0-24 hours after administration.  The radioactivity
    found in liver was 0.07% (0.45 mg/kg) and 0.09% (0.48 mg/kg) and in
    kidney 0.01% (0.4 mg/kg) and 0.02% (0.75 mg/kg) for females and males,
    respectively. The radioactivity in other organs was > 10 times lower. 
    More than 95% of the radioactivity in faeces and urine consisted of
    the unchanged compound. The only metabolite in urine and faeces, Hoe
    061517 (Figure 1), was found to constitute than 3% of the
    adminis-tered dose (Wink  et al., 1986).  Ten male and 10 female
    (2/sex served as controls) SPF Wistar rats, 6 and 9 weeks of age
    respectively, received doses of 2 mg glufosinate ammonium/kg bw daily
    for 14 days, and one dose at day 15 of 2 mg/kg bw of radiolabelled
    test substance (3, 4-14C, 43.6 mCi/g).  No relevant sex dependent
    differences were observed, neither in excretion route nor in excretion
    rate. More than 80% of the applied dose was excreted via faeces and
    approximately 5% via urine during the first 48 h after administration.
    More than 80% of the radioactivity in faeces and urine was the
    unchanged parent compound. Two main metabolites, 3-methylphosphinico-
    propionic acid (< 8% of applied dose) and 3-methylphosphinico-
    3-oxo-propionic acid (<4% of applied dose) were found in urine and
    faeces.  Two minor metabolites were not characterized (Wink  et al.,
    1986b).

         Nine male and 9 female SPF Wistar rats, 10-12 weeks of age
    received one oral dose of 800 mg radiolabelled glufosinate ammonium
    (3,4-14C, 54.1 mCi/g)/kg bw and sacrificed 6 and 24 h after
    administration.  Unchanged substance was present in all samples.  Two
    main metabolites were found in urine and extracts of liver and kidneys:
    3-methylphosphinico-propionic acid and 3 methyl-phosphinico-
    3-oxo-propionic acid.  No sex-related difference was found in
    excretion not metabolism (Schwalbe-Fehl  et al., 1985).

         Groups of 15 female SPF Wistar rats, 10-12 weeks of age were
    dosed orally with 10 or 100 mg glufosinate ammonium (purity: 99.6%)/kg
    bw/day for 10 days. For the administration on the days 1, 8, 9 and 10,
    radiolabelled substance (3,4-14C, 47.7 mCi/g) was used. Different
    groups of the animals were sacrificed after 24 and 48 hours.  The
    administrated radioactivity was rapidly excreted mainly via faeces
    (73-103%), less than 5% was eliminated via urine. Repeated dosing did
    not influence the route nor rate of excretion. The major part of
    excreted radioactivity consisted of unchanged substance. Two
    metabolites were detected in urine and faeces;  3-methylphosphonico-
    propionic acid and 3-methyl-3-oxo-propionic acid in amounts of 5% and
    1% of excreted radioactivity respectively. Liver, kidneys, spleen and
    brain contained less than 0.1% of the total administrated

    radioactivity at all sacrifice dates.  Excretion and characterization
    of these radioactive residues demonstrated the presence of unchanged
    substance (68-81 %) and the metabolite 3-methylphosphinico-propionic
    acid (20-32%) (Schwalbe-Fehl  et al., 1986). 

         Analysis of radioactivity in liver and kidney of laying hens
    after repeated oral administration of an equimolar mixture of
    radiolabelled glufosinate ammonium and its major metabolite,
    3-methylphosphinico-propionic acid was performed (see Ellgehausen
     et al., 1984 in section "Absorption, distribution and excretion"). 
    Eight hours after the final administration only the metabolite was
    found. After 24 hours the radioactivity present was too low for
    further analysis (Ellgehausen, 1986).

    Effects on enzymes and other biochemical parameters

         Glufosinate ammonium (purity 95.3%) was administered once orally
    (in deionized water, 10 ml/kg bw) in doses of 0, 50 or 200 mg/kg bw to
    groups of female SPF NMRI mice with an average weight of 17.7 g. 
    Zero, 200 and 800 mg/kg bw was administered to female SPF Wistar rats
    weighing an average of 203.0 g.  The animals were killed 4 hours after
    dosing.  No deaths or clinical signs of intoxication were observed. 
    One single treatment with doses up to the sublethal range did not
    cause inhibition of glutamine synthetase activity in the brain or any
    change in the NH4+, glutamine or glutamic levels in this organ (only
    the latter two parameters were measured in rats).  However, in the
    kidneys of both species in both doses and in the liver of top-dosed
    rats,  there was a marked inhibition of glutamine synthetase activity,
    accompanied by an increase of NH4+ level in liver in top-dosed mice. 
    No changes of glutamine and glutamic acid were observed in liver of
    rats, the only species analyzed in this study (Ebert & Kramer, 1985).

         Glufosinate ammonium (purity 96.9%) intravenously administrated
    to rats (strain not specified) in a single dose of 10 or 100 mg/kg bw
    caused a slight decrease in glutamine synthetase activity in the
    brain. No changes were found in catecholamine concentrations in
    frontal cortex, striatum or hippocampus (Gerhards & Köcher, 1986).

         Glufosinate ammonium (purity 92.5%) was administered in the diet
    to groups of 10 male and 10 female F344/Du CrJ rats (4 weeks of age at
    arrival) for 13 weeks in concentrations of 0, 8, 64, 500 or 4000 ppm. 
    Half of the animals in the respective groups were killed at the end of
    the dosing period, the other half after a 4 week recovery period.  An
    inhibition of glutamine synthetase activity in the liver was found at
    the end of the dosing period in top-dosed males and in the females
    dosed with 500 or 4000 ppm.  No effect was found after the 4 week
    recovery period.  No treatment-related effect was found on serum
    levels of ammonia (Ohashi  et al., 1982).

         Glufosinate ammonium (purity 96.9%) was administered once orally
    by gavage in deionized water, 10 ml/kg bw to groups of 15 or 30 (in
    the top-dose) female SPF Wistar rats, 8-9 weeks of age in doses 0,
    200, 800 and 1600 mg/kg bw.  One-third of the animals in the groups
    was killed 24 hours, 3 or 7.5 days after dosing respectively.  The
    animals dosed with 200 and 800 ppm exhibited a very slight impairment
    of behaviour (reduced motivation and performance), which diminished
    increasingly towards the end of the examinations. One animal in the
    800 mg group killed at day 1 had convulsions.  The top-dosed animals
    exhibited different degrees of signs of CNS excitability (tendency to
    convulsions and spasms).  Three animals died. These clinical signs
    receded during the course of the study.  A marked inhibition of
    glutamine synthetase was observed in liver and kidneys in all treated
    animals and in brain in high dose animals.  An increase in glutamate
    level was only observed in the liver and was significant in high dose
    animals one day after dosing.  A decrease was seen in the brain which
    was statistically significant in animals dosed with either 800 or 1600
    mg, 7.5 days after dosing. However, clear evidence for an increase in
    the level of NH4+in these organs could not be established.  A
    borderline effect on behaviour was reported in the animals dosed at
    200 mg/kg bw (Ebert  et al., 1986c).

         Glufosinate ammonium (purity 96.9%) was administered to groups of
    40 male and 40 female SPF Wistar rats approximately 6 weeks of age in
    the diet at doses of 0, 40, 200, 1000 and 5000 ppm.  Analysis showed
    that the actual concen-trations of active ingredient were 32-35,
    173-184, 803-896, and 4285-4576 ppm for the 4 doses respectively, and
    that the substance remained satisfactorily stable in the diet for 30
    days. The actual calculated doses were 0, 3.7, 18.7, 93.5 and 443
    mg/kg bw/day for males and 0, 3.7, 18.3, 89.4 and 424 mg/kg bw/day for
    females.

         Glufosinate ammonium (purity 96.9%) was administered to groups of
    40 male and 40 female SPF Wistar rats approximately 6 weeks of age in
    the diet at doses of 0, 40, 200, 1000 and 5000 ppm.  The actual
    calculated doses were 0, 3.7, 18.7, 93.5 and 443 mg/kg bw/day for
    males and 0, 3.7, 18.3, 89.4 and 424 mg/kg bw/day for females.  Ten
    animals/sex/group were killed 0, 3, 7 and 28 days after last day of
    dosing.  Treatment-related behavioural changes (hypersensitivity,
    excitation of the autonomous nervous system, subnormal temperature,
    convulsions) were observed in high-dose animals.  No effects on
    behaviour nor on various parameters reflecting the function of the
    central, peripheral and autonomous nervous system nor general
    intoxication were observed at 1000 ppm.  Bodyweight gain was only
    affected in top-dosed males.  An initial reduction in food intake and
    an increase in water consumption was observed in high-dose animals. 
    The macrosocopic findings revealed no differences between the groups. 
    Kidney weights were increased in top-dosed females.  Determination of
    the catecholamine transmitters in the brain, revealed a slight,
    statistically significant lowering in dopamine only in top-dosed

    females.  A dose-related inhibition of glutamine synthetase was found
    in males and females dosed 200 to 5000 ppm in liver, in top-dosed
    males in the brain and in males doses at 200 to 5000 ppm in the
    kidneys.  None of the changes in glutamine synthetase was present
    after 28 days of recovery.  Determination of NH+ in brain, liver and
    kidneys did not reveal any treatment-related changes.

         No effect of the substance was seen on aspartate, glutamate,
    asparagine and glycine in either brain, liver or kidneys.  However,
    the examination of glutamine revealed a decrease in free amino acid
    level, statistically significant in the liver in the 200, 1000 and
    5000 ppm groups and in the brain and kidneys in the 5000 ppm group. 
    After a 3-day treatment-free period this effect on glutamine was not
    present.  No indication of changes could be found in alanine in the
    liver or taurine in the brain.  None of the parameters examined
    (isocitrate-DH (NADP-dependent), succinate-dehydrogenase, maleate
    enzyme (decarboxylating), fructose diphosphatase or glycogen) yielded
    any indication of substance-related changes in energy and carbohydrate
    metabolism.  Glutamate pyruvate transaminase was lowered in males in
    the three highest dosage groups at the end of the treatment, which may
    have been due to an exceptionally high activity of the controls.  No
    treatment-related changes were observed on glutathione level nor
    gamma-glutamyltranspeptidase.  No substance-related changes were found
    in glutamate oxaloacetate transaminase nor glutamate dehydrogenase. 
    Glutamate pyruvate transaminase was reduced in males dosed at 200 ppm
    and greater.  However, the figures exhibited no marked
    dose-relationship and were within normal range.  Alanine level in the
    liver revealed no change.  The NOAEL is 40 ppm equal to 3.7 mg/kg
    bw/day (Ebert  et al., 1986b).

         In two studies, in which groups of 10 male and 10 female Wistar
    rats, weighing 167-227 g were administered single lethal doses by oral
    gavage, no therapeutic effect of ip treatment with atropine sulfate
    and pyridine-2-aldoxim methiodide was observed.  Phenobarbital-sodium
    proved an efficient therapeutic agent (Ebert & Weigand, 1983; Ebert &
    Leist, 1986).

         Glufosinate ammonium (purity 95.3%) was administered orally (by
    capsule) to groups of 6 male and 6 female Beagle dogs, 5-8 months of
    age in doses 0, 1 and 8 mg/kg bw/day for 18 days followed by 10 days
    similar dosing with labelled glufosinate ammonium (3,4-14C, 54.1
    mCi/g).  One animal/sex/group was sacrificed on days 18, 19 and 28 of
    treatment and on days 1, 2 and 4 of the recovery period.  Parameters
    including blood chemistry, haematology, neurological parameters and
    histopathology were examined.  No animal died during the study. 
    Neurological examinations showed only slightly increased motor
    activity in high-dose animals.  Females exhibited a slightly lower
    food intake, and body weight gain was supp-ressed in male and female
    high-dose animals (in the first week and after the first week -

    females only).  A slight decrease in haematocrit, eryrthrocyte count
    and haemoglobin was seen in treated females and less pronounced in
    males after 28 days treatment and at the end of the recovery period
    was considered to be a secondary effect and not treatment related.  No
    treatment-related changes were found in standard biochemical
    parameters.  A slight, dose-correlated but not significant decrease in
    brain cholinesterase was seen in males only at 28 days of treatment. 
    However, no treatment-related changes were noted in cholinesterase
    activity or in thyroid function, acid-base parameters, glutathione
    levels in whole blood, glucose-6-phosphate dehydrogenase and
    glutathione reductase levels in whole blood nor amino acids in the
    plasma.  Analysis of tissue extracts showed a decrease in aspartic
    acid, glutamic acid, glutamine, glycine and taurine in brain stem,
    aspartic acid, phosphoethanolamine, glutamine synthetase and an
    increase in alpha-ketoglutarate in cerebellum, an increase in
    phosphoethanolamine and a decrease in glutamine-synthetase in the
    midbrain and a decrease in threonine and glutamine-synthetase in
    spinal cord in the top-dosed males. In low-dosed males the only
    changes were seen in phosphoethanolamine and threonine in cerebellum
    and spinal cord, respectively. In high-dose females, the following
    were observed to decrease;  glutathione, arginine and
    glutamine-synthetase in midbrain, aspartic acid, glutamine,
    phosphoethanolamine and taurine in brain stem, arginine and
    alpha-ketoglutarate in spinal cord, phosphoethanolamine, taurine, and
    glutamine-synthetase.  An increase was observed in alpha-ketoglutarate
    in cerebellum and glutamine, phosphoethanolamine and taurine in
    cortex.  Changes were found in arginine in spinal cord and in
    phosphoethanolamine and taurine in the cortex.  In heart, a decrease
    was observed with glutamine in both doses and in taurine in the
    high-dose females.  No changes were seen in urinanalysis and no
    treatment-related effect was noted in the pathological examinations. 
    The substance caused marginal signs indicative of increased
    stimulation of CNS in top-dosed animals. However, no changes of
    excitatory and inhibitory amino acid neurotransmitters or
    catecholamine neurotransmitters were noted.  The NOEL for the
    neurological system and physiological homeostasia is 1 mg/kg bw/day
    while the top-dose can be considered threshold dose level for an
    effect on physiological function (Sachsse, 1986).

         In an  in vitro study of phosphonic analogs of glutamic acid
    2-amino-4-(methylphosphino)butyric acid was shown to be a strong
    inhibitor of rat brain glutamate decarboxylase (Lacoste  et al.,
    1985).

         In an  in vitro study with phosphonic analogues of glutamic acid
    it was shown that these compounds competitively inhibit rat liver
    glutamine synthetase (Lejczak  et al., 1981).

         Glufosinate ammonium was investigated in a number of  in vitro
    receptor binding assays.  No significant effect was found in either
    transmitter receptors GABA, noradrenalin-alpha2, noradrenalin-beta,

    dopamine and serotonin nor in other binding sites (calcium ion channel
    and benzodiazepine) (Schacht, 1986).

         In an  in vitro study, glufosinate ammonium (purity: 99.5%) was
    added to mitonchodria of livers of Wistar female rats weighing
    140-180 g.  When the substrate was preincubated with substance for 10
    minutes at 25 °C or 120 minutes at 0 °C, no block of the oxidative
    consumption was measured.  Either the substance has no direct influence
    on the metabolism of intact rat liver mitochondria or the substance was
    not been taken up by these organelles (Metzger, 1986).

          In vitro studies on effect of glufosinate ammonium or
    DL-homoalanin-4-yl(methyl)-phosphinic acid on glutamate oxalacetate
    transaminase, glutamate pyruvate transaminase and gamma-glutamyl
    transpeptidase from the pig and glutamate dehydrogenase from the
    bovine liver showed, with bovinal liver glutamate dehydrogenase only,
    a 19 or 15% reduction in activity due to the test substances (Köcher
    & Schulze, 1986).

    Toxicological studies

    Acute toxicity
        Table 1.  Acute toxicity of glufosinate-ammonium

                                                                                     

                        LD50 or LC50 (mg/kg bw)
                                                                                     
    Species             Males               Females        Reference
                                                                                     

    LD50 (po)

    Mouse               431a                               Mayer & Weigand (1980a)
                        436b                               Inoue & Okamura (1982a)

                                            416a           Mayer & Weigand (1980b)
                                            464b           Inoue & Okamura (1982a)

    Rat                 2000c                              Mayer & Weigand (1980c)
                        1660d                              Ohtaka et al. (1981a)

                                            1620c          Mayer & Weigand (1980c)
                                            1510d          Ohtaka et al. (1981b)

    Doge                >200                               Mayer & Kramer (1980)
                                            >400
                                                                               

    Table 1 (contd).

                                                                               

                        LD50 or LC50 (mg/kg bw)
                                                                                     
    Species             Males               Females        Reference
                                                                                     

    LC50 (percutaneous)

    Rat                 >4000c                             Mayer & Weigand (1982a)
                                            4000c          Mayer & Weigand (1982b)

    Rabbitf             2000                               Parcell & Kynoch (1986)
                                            2000

    LC50 (inhalation)

    Aerosol: Ratc
                        >0.621 mg/l                        Hollander & Weigand (1982)

                                            >0.621 mg/l    Hollander & Weigand (1982)

    Dust:               1.26 mg/l                          Hollander & Weigand (1982)
    Ratc                                    2.60 mg/l      Hollander & Weigand (1982)

    LD50 (ip)

    Mouseb              103                                Inoue & Okamura (1982c)
                                            82             Inoue & Okamura (1982c)

    Rat                 96d                                Ohtaka et al. (1981c)
                        204c                               Mayer & Weigand (1982c)
                                            93.2c          Mayer & Weigand (1982d)
                                            83d            Ohtaka et al. (1981d)

    LD50 (sc)

    Mouse               88b                                Inoue & Okamura (1982c)
                                            104b           Inoue & Okamura (1982c)
     
    Rat                 73d                                Ohtaka et al. (1981f)
                                            61d            Ohtaka et al. (1981g)
                                                                                     

    a  =  NMRI, SPF            d  =  F344
    b  =  ICR, SPF             e  =  Beagle
    c  =  Wistar, SPF          f  =  NZW
    
    Short-term studies

    Mice

         Glufosinate (purity: 95.3%) was administered to groups of 10 male
    and 10 female SPF NMRI mice, 5 weeks of age, in their diet in
    concentrations 0, 80, 320 and 1280 ppm for 13 weeks. The calculated
    mean doses were 0, 17, 67 and 278 mg/kg bw/day and 0, 19, 87 and 288
    mg/kg bw/day for males and females, respectively. Analysis for
    homogeneity of substance in diets were approximately within +/- 15%
    and mean concentrations were 0, 119, 82 and 92%, respectively.  The
    subst ance is stable in the diet at room temperature at levels of
    50-5000 ppm.  No sign of systemic toxicity was observed in any animal.
    The mean body weights of treated animals were comparable to those of
    the controls and no relevant, dose-related changes were seen in food
    consumption or ophthalmoscopic inspection.  Apart from an increase in
    monocyte-count in high dose males, no significant compound-related
    effect was found in any haematological measurements. Alkaline
    phosphatase was elevated in high-dose females.  A slight increase in
    aspartate aminotransferase in high-dose males and an increase in
    potassium in males in the 1280 and 320 ppm groups were seen.  A
    dose-dependent increase was noted in absolute organ weights, organ to
    body weight ratios and organ to brain weight ratios in the liver and
    kidneys which was only statistically significant in the liver to body
    weight ratio in high dose males. No treatment-related pathological
    findings were noted.  The NOAEL is 80 ppm corresponding to 17 and 19
    mg/kg bw/day for male and female mice, respectively (Suter & Sachsse,
    1984b).

    Rats

         Groups of 10 male and 10 female F344 rats, 5 weeks of age, were
    administered glufosinate ammonium (purity: 92.1%) in the diet at
    dosage levels of 0, 8, 16, 32, 64, 320 and 3200 ppm for 2 weeks.  The
    mean doses were 0, 0.7, 1.4, 2.9, 5.8, 28.5 and 262 mg/kg bw/day for
    males and 0, 0.8, 1.7, 3.3, 6.6, 33.7 and 296 mg/kg bw/day for females
    based on food consumption and nominal concentrations.  No effect was
    observed in the clinical condition of the animals. Body weight gain
    was suppressed and food consumption and efficiency and water
    consumption were decreased during the first week in high dose animals. 
    No dose-correlated changes were noted in haematological investigation
    or urinalysis.  Apart from a decreased LDH activity in females in the
    3200 ppm group, no compound-related effects were observed. The
    absolute weights of heart, lung, liver and spleen in both sexes and
    the ovaries in females dosed 3200 ppm were lower when compared to
    those of the controls.  For the heart and the ovaries in high dose
    females, a concomitant effect was noted in relative organ weight.  No
    changes related to the administration of the compound were observed in
    any other groups (Ohtaka & Nakayoshi, 1981).

         Groups of 5 male and 5 female SPF Wistar rats, 5-6 weeks of age
    were administered glufosinate ammonium (purity: 93.5%) in the diet at
    dosages 0, 50, 500, 2500 and 5000 ppm for 28 days.  Analysis showed
    the actual concentrations to be 0, 101.1%, 95.3%, 92.7% and 105.9%
    respectively, and the homogeneity to be within +/- 15%. The compound
    remained stable at all levels over a 21-day period at room
    temperature.  No signs or symptoms of systemic toxicity were observed.
    Slightly reduced food consumption and a corresponding decrease in food
    conversion in the start of the study were seen in animals in the 2
    highest dosage groups. No treatment-related effects were noted in
    haematology, clinical biochemistry or urinalysis.  Statistically
    significant increases in relative kidney weights were seen in males in
    2500 ppm group and in all dosed females, although the increases did
    not appear to be dose-related.  Apart from reddening of the gastric
    mucosa in 4 out of 5 males in the 5000 ppm group, no treatment-related
    macroscopic or microscopic findings were noted.  The NOAEL is 500 ppm,
    equivalent to 53 mg/kg bw/day for males and 58 mg/kg bw/day for
    females (Suter & Sachsse, 1984).

         In a 13-week toxicity study, glufosinate ammonium (purity: 92.1%)
    was administered in the diet to groups of 30 male and 30 female F344
    rats, 5 weeks of age, at dosage levels of 8, 64, 500 and 4000 ppm
    (concentrations were found to be 7.5-7.8, 57.7-68.5, 469-547 and
    3910-4150 ppm in an analysis for homogeneity).  Ten animals of each
    sex were sacrificed after a 4-week withdrawal period.   The actual
    calculated doses were 0.5, 4, 32 and 263 mg/kg bw/day for males and
    0.6, 5, 39 and 311 mg/kg bw/day.  Apart from the death of one

    high-dose male on day 71 with a miliary tumour in the thoracic cavity,
    no treatment related changes were observed. Body weight gain was
    suppressed in top-dosed animals in the first 3 weeks and a concomitant
    decrease in food consumption was noted.  Water consumption was
    decreased in animals of both sexes dosed with 4000 ppm during the
    first week of administration and was thereafter increased in males
    until termination of administration.  Increased water consumption was
    not observed during the recovery period.  No dose-related changes were
    found in haematological investigation. Blood chemistry after 47 days
    showed a slight dose-related decrease in calcium and a decrease, not
    dose-related, in uric acid in all treated males. The corresponding
    investigation in females revealed a decrease in LDH, total bilirubin, 
    Cl and direct bilirubin in high-dose animals, an increase in albumin
    and A/G (Albumin/Globulin) in the two highest dosage groups and the
    low-dose group and an increase in creatinine in the 64 ppm and 4000
    ppm groups.  After 13 weeks, cholesterol was increased in high-dose
    males and uric acid decreased in a dose-related manner in all treated
    males, while no significant changes were found in females.  Liver
    glutamine synthetase in liver decreased significantly in top-dosed
    animals of both sexes and in females dosed at 500 ppm after 13 weeks,
    however, returning to normal after a 4-week recovery period. No
    dose-related changes were found in serum levels of ammonia. Urinalysis
    showed a decrease in pH in high-dose animals and an increase in
    specific gravity in females fed 4000 ppm. The pH remained low in
    high-dose animals of both sexes after the 4 week recovery period.  No
    compound-related changes were found at necropsy.  Absolute and
    relative kidney weight were increased in males and females in all dose
    levels except the low dose in which males had an increase in absolute
    weight. The effect in kidneys was present even after a 4 weeks
    recovery period with both absolute and relative weights being affected
    in males in the two highest dosage groups. Other changes in organ
    weight were increased thymus weight in the 500 ppm and the 4000 ppm
    group and an increase in the weight of the adrenals in all treated
    males and a decrease in both absolute and relative brain weights in
    females dosed 500 and 4000 ppm after 13 weeks. No compound-related
    effects were observed in the histological examination.  The NOAEL was
    64 ppm for males equivalent to 4.1 mg/kg bw/day and 500 ppm for
    females, equivalent to 39 mg/kg bw/day (Ohtaka  et al., 1981g).

    Dogs

         Groups of 4 male and 4 female Beagle dogs, 33-37 weeks old, were
    fed glufosinate (purity 92.1%) in dietary concentrations 0, 4, 8, 16,
    64 or 256 ppm for 13 weeks. The calculated doses were 0, 0.1, 0.3,
    0.5, 2, and 7.8 mg/kg bw/day, respectively.  Analysis for homogeneity
    of the substance in diet was acceptable and the compound remained
    stable in the diet for a period of 2 weeks at room temperature.  
    Apart from 2 high-dose males which exhibited aggressive behaviour, no
    treatment-related changes in behavior or health condition were
    observed.  A slight reduction in body weight occurred in high-dose
    females and food intake was slightly diminished in high-dose animals

    of both sexes.  Water intake was similar in all groups.  No
    treatment-related changes were noted in opthalmoscopy, haematology,
    clinical chemistry or urinalysis.  Organ weights showed no marked or
    statistically significant differences between the various test groups
    and the controls.  Both the absolute and relative weights of the
    thyroids were lowered in all test groups, especially in the 64 and 256
    ppm groups of females.  Gross and microscopic examination did not
    reveal any abnormalities considered to be of toxicological
    significance.  The NOAEL was 64 ppm, equal to 2 mg/kg bw/day (Til & de
    Groot, 1982).

         Glufosinate ammonium (purity 95.3 %) was administered to groups
    of 4 male and 4 female Beagle dogs, 4-6 months of age in the diet at
    levels equal to 0, 1.8, 4.5 and 8.4 mg/kg bw/day for 6 or 12 months.
    The high dose was adjusted from 10.8 to 8.4 mg on day 11 and
    afterwards.  Tests showed homogeneity to be within +/- 10 %, and
    stability of the substance in the diet up to 21 days at room
    temperature. Clinical symptoms manifested by triasmus, salivation and
    hyperactvity followed by somnolence and hypoactivity, as well as
    stereotypic gait, tremor, ataxia, whining, urinating, and tonic-clonic
    spasms were seen in one male and two females receiving the high dose
    between days 9 and 14 of treatment.  Two of these animals died, one of
    each sex, and the one male was replaced by another male, which was
    treated for 12 months.  The deaths of the two dogs in the highest
    dosage group were caused by heart and circulatory failure due to
    myocardial necrosis.  Low-dosed females showed a decrease in food
    intake, whereas food intakes for the mid- and top-dosed females were
    increased when compared to controls.  No changes were seen in males
    apart from a decrease in food consumption during the first week of
    treatment.  The mean body weight gains of the treated males,
    especially high-dose males, was slightly reduced during the first 6
    months of treatment. No dose-related changes were found in hearing
    tests, ophthalmoscopic examinations or examinations of teeth and
    membranes.  Electrocardiogram (ECG) values showed some increase in P
    wave (P wave ampl. =  0.6 mV, upper normal limit = + 0.45 mV) in one
    high-dose male after 12 months and this effect is characterized as a
    questionable compound-related effect.  A slight decrease in heart
    rate, within the normal range, was observed in groups receiving the
    test compound after 6 months in the highest dosage group. Haematology,
    clinical biochemistry and urinalysis indicated no changes of
    toxicological significance, the variations being within the range of
    values of historical controls.  No treatment-related changes in organ
    weights were noted. The pathomorphological findings that were reported
    are considered to be spontaneous lesions usually observed in dogs of
    this strain and age.  The NOAEL in this study is 5 mg/kg bw/day
    (corrected value is 4.5 mg) for dog (Bathe & Sachsse, 1984).

    Rats (Metabolites)

         3-methylphosphinico-propionic acid (purity >99%), the principal
    metabolite in plant residues and also a relevant metabolite in

    mammalian organisms, was administered in the diet to groups of 5 male
    and 5 female SPF Wistar rats, average weight 103 g and 102 g
    respectively for 28 days in concentrations 0, 50, 500, 2500 and 5000
    ppm.  Analysis showed stability of the test substance in the diet for
    a period of 30 days and concentrations corresponded satisfactorily to
    the nominal concentrations; 36-51, 359 and 3660-4914 ppm. The
    calculated doses were 0, 6, 57, 286 and 554 mg/kg bw/day for males and
    0, 6, 55, 282 and 561 mg/kg bw/day for females.  No substance-related
    effect was found in behaviour, clinical observations or body weights,
    food intake and water consumption.  Changes in haematological
    parameters gave no indication of substance-related effects.  An
    increase in uric acid in high-dose males and in triglycerides in
    top-dosed females, which was within normal biological variation, were
    the only treatment-related changes found in clinical chemistry.  Apart
    from the appearance of the urine (clear and light to dark yellow in
    colour), no substance-related effects were observed on urinalysis. 
    Glutamine synthetase activity in the liver was unaffected by
    treatment.  Apart from an increase in liver weights in top-dosed
    females, the pathological examinations did not reveal any effect. 
    Histological examinations were performed in controls and high-dose
    animals only.  The NOAEL is 2500 ppm equivalent to 284 mg/kg bw/day
    (286 for males and 282 for females) (Ebert  et al., 1986a).

    Long-term/carcinogenicity studies

    Mice

         Glufosinate ammonium (purity 95.3%) was administered for 2 years
    in the diet to groups of 50 male and 50 female SPF NMRI mice, 5-6
    weeks old in levels 0, 20, 80, ppm and 160 ppm for males and 0, 20,
    80, and 320 for females. In addition, 10 mice/sex/group were dosed for
    52 weeks. The calculated doses were 2.8, 10.8 and 22.6 mg/kg bw/day
    and 4.2, 16.2 and 64 mg/kg bw/day, respectively (animal dosed 2
    years).  Analysis of the diets showed the mean concentrations to be
    103%, 99% and 99% of nominal doses in the low, medium and high level. 
    Homogeneity varied in the range of + 20% to - 18% and the substance
    remained stable in the diets for 21 days at room temperature.  The
    mortality rate in top-dosed males during the study was significantly
    increased and this was considered treatment-related even though the
    cause of higher mortality could not be established. No
    treatment-related clinical symptoms nor signs of toxicity were noted.
    Body weights were lowered in high-dose males scheduled for sacrifice
    at week 52, and in high-dose females between weeks 7 and 31.  Food
    intake was not affected. Ophthalmoscopic examinations, hearing tests
    and examination of teeth and mucous membranes revealed no
    treatment-related effects.  No changes of toxicological significance
    were noted in haematological values. Clinical biochemistry showed a
    slight increase in glucose level in top-dosed animals at week 52, an
    increase in aminotransferase in top-dosed females after 52 weeks and
    a decrease in glutathion level in top-dosed males after 104 weeks of
    treatment.  Other changes were within the range of biological

    variation of historical controls.  After 52 weeks treatment the
    absolute and relative spleen weight in top-dosed females was slightly
    but not significantly increased.  After 104 weeks of treatment, no
    treatment-related organ weight changes were detected.  Neoplastic and
    non-neoplastic lesions noted in this study were commonly observed in
    mice of this strain and age, and the type and incidence were
    considered to be similar in treated and control animals.  The NOAEL is
    80 ppm, equivalent to about 11 mg and 16 mg/kg bw/day for males and
    females, respectively (Suter & Sachsse, 1986b).

    Rats

         Groups of 80 male and 80 female SPF Wistar rats, 5 1/2 weeks of
    age, were administered glufosinate ammonium (purity: 95.5%) in test
    diets in concentrations of 0, 40, 140 and 500 ppm for 52 weeks (10
    rats/sex/group), 104 weeks (20 rats/sex/group), or 130 weeks (50
    rats/sex/group). The doses for males and females were 0, 2.1, 7.6 and
    26.7 mg/kg bw/day.  Analysis showed the mean concentrations to be 96,
    97 and 99% of the nominal doses respectively and homogeneity varied in
    the range of +/- 22% of mean concentration. The substance remained
    stable over a period of at least 21 days, at room temperature. 
    Females in the 140 and 500 ppm groups displayed a significantly
    increased intercurrent mortality.  Treatment-related clinical signs of
    toxicity were not observed.  No effect was seen in ophthalmoscopic
    examinations, hearing test nor examination of teeth and mucous
    membranes.  Body weights of males dosed at 140 and 500 ppm were
    increased in males on weeks 6-51 and weeks 10-51, respectively.  Food
    consumption was com-parable between groups when expressed in g/kg
    bw/day.  Females dosed at 140 and 500 ppm showed an increase in body
    weight in weeks 4-35 and weeks 4-79, respectively. Food intake in g/kg
    bw/day was similar in all groups.  A decrease in erythrocyte count,
    haemoglobin concentrations and haematocrit value were noted in
    top-dosed animals only after 52 weeks of treatment.  Special
    biochemical investigations on liver, kidneys and brain showed a slight
    inhibition of liver and brain glutamine synthetase activity in animals
    dosed at 140 and 500 ppm at week 52 and in weeks 52 and 104,
    respectively. The kidney glutamine synthetase activity was slightly to
    moderately increased in animals in all dosage groups.  Ammonia levels
    were unaffected in all treatment groups. Glutathione (GSH, reduced;
    GSSG, oxidized) in liver was lowered in males (GSSG) and in females
    (GSH and GSH+GSSG) in groups dosed at 140 and 500 ppm.  GSH in blood
    was decreased in top-dosed animals and in females dosed at 140 ppm,
    and GSSG was up in high-dose males. Changes in other biochemical
    parameters were all within the range of normal biological variation. 
    Absolute and relative kidney weights were slightly increased in males
    dosed at 140 and 500 ppm and in top-dosed females.  At week 130 a
    slight increase in relative kidney weight was noted in all treated
    females.

         An increased incidence of benign medullary tumours (adrenal
    gland) was observed in males at 130 weeks.  However, a positive trend
    was not found in statistical analysis.  No other treatment-related
    effect was found in the pathological examination.  The substance is
    not oncogenic in rats in doses up to 500 ppm equivalent to 24.4 mg/kg
    bw/day.  The NOAEL in this study is 40 ppm equivalent to 2.1 mg/kg
    bw/day (Suter & Sachsse, 1986a).

    Reproduction studies

         In a preliminary study to the multigeneration study, glufosinate
    ammonium (purity 95.3%) was administered in the diet to groups of 10
    male and 10 female SPF Wistar rats, 8-9 weeks of age in dose levels 0,
    50, 500, 2500 and 5000 ppm during a three-week premating period
    continuing throughout the mating, gestation and lactation period. Mean
    concentrations were found to be in the range 78-83%, 87-89%, 93-97%
    and 90-91% of nominal doses, respectively. Homogeneity of all samples
    was found to be 5.1 +/- 2.2%.  Supplementary groups of 10 males were
    dosed 0, 500, 2500 and 5000 ppm for 9 weeks and during the period of
    mating with non-dosed females.  No signs of toxicity nor clinical
    symptoms were noted in any animal in any group. Food consumption was
    reduced in the premating period in males in the 2500 and 5000 ppm
    groups and in high dose females.  Reduction in food consumption was
    recorded in females in the 2500 and 5000 ppm groups during gestation
    and only the low-dosed females and the controls had comparable food
    intake during lactation.  A slight, significantly reduced body weight
    was noted in high-dose males in the premating period. In the gestation
    and lactation period only the low-dose females and their controls
    showed overall comparability.  Duration of gestation in the 500 pm
    group was 0.9 day less than that of the controls. Females in the 2500
    and 5000 ppm groups delivered no pups, although implantation sites
    were noted.  A significantly increased post-implantation loss was seen
    in dams of the 500 ppm groups. The findings in the supplementary
    groups showed that the effect on reproduction was mediated via the
    dams.  The NOAEL was 50 ppm.  Based upon this study, doses of 40, 120
    and 360 ppm were selected for the multiple-generation study (Becker &
    Sachsse, 1986).

         In a two-generation study, groups of 30 male and 30 female SPF
    Wistar rats, 7 weeks of age (F0) were administered glufosinate
    ammonium (purity 95.3%) in their diet in concentrations 0, 40, 120 and
    360 ppm for a period of 80 days preparing and during pairing,
    gestation and lactation for breeding of the F1a and F1b groups.  The
    F1b rats were dosed similarly to the F0 for a period of 101 days
    including lactation for breeding F2a and F2b. Analysis showed the
    concentration of the test substance in the diet to be 109, 102, and
    104% of the nominal concentrations 40, 120 and 360 ppm respectively. 
    Homogeneity varied between +16% to -17%, and the substance was stable
    for 21 days at room temperature. Concentration of the metabolites (see
    Biotransformation) was lower than 0.2% during a period of 6 months.

    A slightly reduced food intake was noted in F0 and F1 high-dose
    females during lactation periods. There was a decrease in litter size
    in the 360 ppm group, and increased weights of kidneys in males dosed
    at 120 and 360 ppm and in top-dosed females. No other treatment-
    related changes were found.  The NOAEL for reproduction was 120 ppm
    (equivalent to 12 mg/kg bw) due to reduced litter size in the
    top-dosed group (Becker & Sachsse, 1987).

    Special studies on embryotoxicity

         Glufosinate ammonium (purity: 97.7%) was administered orally to
    groups of 20 mated female SPF Wistar rats, about 70 days of age in
    doses 0, 10, 50 and 250 mg/kg bw/day (in redistilled water, 5 ml/kg
    bw) days 7-16 of pregnancy (day one = sperm detection). Caesarean
    section was performed on day 21.  Dose-related clinical signs of
    toxicity were observed at all dose levels and consisted of motor
    unrest accompanied in the two highest dosage groups by hyperactivity,
    piloerection, vaginal haemorrhages, and reduction in body weights.
    Average food consumption and body weight gain was lowered in top-dosed
    animals.  Number of dams carrying live fetuses to term in the 50 and
    250 mg groups was 16 and 10, respectively, compared to 20 in low-dosed
    animals and controls. Number of corpora lutea and implantations was
    comparable with that of the controls.  Examination of the fetuses
    revealed a dose-related increased incidence of distension of renal
    pelvis and ureter in all three dose groups, and a slight retardation
    in ossification in the 250 mg/kg bw/day group was observed.  The
    autopsy of the dams revealed no changes in the low-dose group when
    compared with the controls (large adrenals and a noticeable small
    spleen in the 50 and 250 g/kg bw/group were seen in dams with vaginal
    haemorrhages or only dead implantation), and the only effect on organ
    weights (decreased liver weight) was seen in the high dose dams.  No
    NOAEL was identified for maternal or embryonic/fetal toxicity (Baeder
    & Kramer, 1985a).

         Glufosinate ammonium (purity: 97.2%) was administered orally to
    groups of 21-24 mated female SPF Wistar rats, 70 days of age in doses
    0, 0.5, 2.2 and 10 mg/kg bw/day (in distilled water, 5 ml/kg bw) from
    days 7-16 in pregnancy (day 1 = sperm detection). Caesarian section
    was performed day 21.  No clinical signs of intoxication were
    observed. Food consumption and body weights were not affected in any
    dosed groups.  The only malformations observed were a diaphragmatic
    hernia in one control fetus, gastroschisis in one fetus in the 2.24 mg
    group and one fetus with cleft palate and two fetuses in one litter
    from the 10 mg/kg bw/day dose level with haematocysts on both hind
    paws accompanied of aplasia in the corresponding toes.  A slight
    increase in weights of kidneys and spleen was found in high dose dams. 
    The NOAEL for both maternal or embryonic/fetal toxicity is 2.24 mg/kg
    bw/day (Baeder & Kramer, 1985b).

         Glufosinate ammonium (purity: 96.9%) was administered orally to
    groups of 20-25 mated female SPF Wistar rats, 65-70 days of age in
    doses of 0, 0.5, 2.2 and 10 mg/kg bw/day (in distilled water, 5 ml/kg
    bw) from day 7 to 16 in pregnancy (Day 1 = sperm detection). The
    animals were allowed to deliver normally and rear their offspring for
    21 days.  Two dams in the 10 mg group were found in lateral position
    with extended limbs, one on day 7 and one 3 days after treatment.
    Piloerection was observed in two dams in low and mid-dose group and
    one in the high-dose group.  No other disturbances were observed in
    behaviour and general health condition.  The NOAEL is 10 mg/kg bw/day
    for maternal, embryonic and fetal toxicity (Pensler  et al., 1986).

         Glufosinate ammonium (purity: 95.3%) was administered orally to
    groups of 15 mated female Himalayan rabbits, 6-7 months of age in
    doses of 0, 2, 6.3 and 20 mg/kg bw/day (in distilled water, 5 ml/kg
    bw) from day 7-19 in pregnancy (the day of pairing = day 0). Caesarian
    delivery was performed on day 29 of pregnancy and the fetuses were
    kept in an incubator for 24 hours and subsequently examined for
    abnormalities.  A decrease in water consumption and/or quantity of
    faeces was observed between days 13 and 25 of pregnancy in 4 dams in
    the low-dose group, 2 in the mid-dose group, 7 in the high-dose group
    and 1 in the controls.  Premature birth occurred in one animal in the
    6.3 mg group and one in the 20 mg/kg bw/day.  Food intake was
    significantly lowered in the 6.3 and 20 mg groups.  Only in the
    high-dose group was a significant reduction in average body weight
    observed.  The mean number of dead fetuses was significantly different
    than the control group at the high dose level.  Body weight in live
    fetuses of high-dose animals was slightly but significantly reduced. 
    Morphological examination of the offspring revealed no
    treatment-related effect.  An increase in kidney weights was observed
    in the high dose dams.  The NOAEL in rabbit is around 6.3 mg/kg bw/day
    (Baeder & Kramer, 1984).

    Special studies of genotoxicity

    Genotoxicity

    Special studies of neurotoxicity

         Glufosinate ammonium, in a formulation containing 40% active
    ingredient, was administered to groups of 6 Leghorn hens, weighing
    1214-1728 g once orally in the dose 10 000 mg/kg bw with
    administration repeated 21 days after the first treatment with or
    without antidote (10 mg/kg bw atropine + 4 mg/kg bw
    1,1'-oxydimethylenebis (4-formylpyridinium chloride) dioxime)).  No
    substance-related effect was found in tests for neurotoxicity or on
    morphology in brain, spinal marrow and peripheral nerves (Leist &
    Weigand, 1979).


    
    Table 2.  Results of genotoxicity assays on glufosinate-ammonium

                                                                                                                            

    Test system                 Test object            Concentrations    Purity    Results    Reference
                                                                           (%)
                                                                                                                            

    Procaryotic systems
    in vitro

    Ames test (with and         S. typhimurium         5-1000 µg/plate    92.1    Negative    Othaka et al., (1981)
    without activation)         TA98, TA100,           (500 µg/plate
                                TA1535, TA1537,        cytotoxic)
                                TA1538

    Reverse mutation            E. coli WP2H           5-1000 µg/plate    92.1    Negative    Othaka et al., (1981)
    (with and without                                  (500 µg/plate
    activation)                                        cytotoxic)

    Rec assay                   B. subtilis,           50-10 000 µg/      92.1    Negative    Othaka et al., (1981)
                                H17, M45               disc

    Gene conversion/            S. cerevisiae          1000-10 000 µg/    95.3    Negative    Mellano & Milone (1984a)
    DNA repair test             D4                     plate
    (with and without
    activation)

    Forward mutation            Schizosaccharomyces    125-1000 µg/ml     95.3    Negative    Mellano & Milone (1984b)
    test (with and without      pombe
    activation)
                                                                                                                            

    Table 2 (contd).

                                                                                                                            

    Test system                 Test object            Concentrations    Purity    Results    Reference
                                                                           (%)

                                                                                                                            

    Mammalian test systems
    in vitro

    Unscheduled DNA             Primary rat            26.2-5240 µg/ml    95.3    Negative    Cifone & Myhr (1984)
    synthesis assay             hepatocytes

    Forward mutation            Mouse lymphoma         50-5000 µg/ml      95.3    Negative    Cifone & Myhr (1985)
    assay (with and             L51784
    without activation)

    Structural chromosome       Human lymphocytes      1-1000 µg/ml       95.3    Negative    Pirovano & Milone (1985)
    aberration (with and
    without activation)

    Mammalian test systems
    in vivo

    Micronucleus test           Male and female        0, 100, 200 &      96.9    Negative    Jung & Mayer (1986)
                                NMRI mice              350 µg/g bw
                                (15/sex/group)         (period: 10 ml/
                                                       kg bw)
                                                                                                                            
    

    Special studies on pharmacological actions

    Mice, rabbits and guinea-pigs

         Pharmacological actions of glufosinate ammonium (purity: 97%)
    were investigated in mice, rabbits and guinea-pigs SPF ICR male and
    female mice weighing 30-40 and 20-30 g, respectively, were
    administered a single peroral dose of 0, 200, 400, 800 and 1600 mg
    glufosinate ammonium (in isotonic sodium chloride solution/kg bw. 
    Neuropharmacological changes (multidimensional observation) were
    measured in groups of 3 mice of each sex.  Male mice dosed with 800 mg
    or above and females dosed with 400 mg or above showed signs
    indicating CNS excitation after a latency period of 8 hours. 
    Hexorbarbital sleeping time was measured in groups of 10 males/group.
    Prolonged sleeping time was observed in animals dosed with 800 mg.

         SPF male rabbits of a Japanese white strain weighing 2.5-3.5 kg,
    3 animals/group were administered (in isotonic sodium chloride
    solution, 1 ml per kg bw) a single intravenous dose of 0, 2.5, 10 or
    40 mg glufosinate ammonium.  Neurological signs such as convulsion,
    decreased spontaneous activity, motor incoordination were observed
    after a latency period of 8 hours in high dose animals.  Abnormal EEG
    indicating convulsions appeared more than 4 hours after dosing in
    animals at 10 or 40 mg/kg bw.  The effect disappeared almost within 4
    days.  Body temperature was increased 1-2 °C in 2 top-dosed animals 8
    hours and 1 day after dosing, respectively.  A decrease in respiratory
    rate and an increase in respiratory tidal volume was observed. Blood
    pressure and ECG were unaffected.  Glufosinate ammonium had no effect
    on contraction of anterior tibialis muscle caused by direct or
    indirect stimulations.

         Effect of the substance on haemolysis and blood coagulation was
    investigated in an  in vitro study using blood from rabbits.  No
    treatment-related effect was seen on haemolysis, prothrombin time nor
    activated partial thromboplastin time at doses of 10-5, 10-4 or 10-3
    g/ml.  No effect of the substance on isolated guinea-pig  vas deferens
    (male Hartley, SPF, 6 weeks of age) was observed at doses 10-5, 10-4
    or 10-3 g/ml. However, the high concentration increased the
    noradrenaline or high K+-induced contraction of the  vas deferens. A
    concentration of 10-3 g of the substance/ml increased the muscle tone
    and the spontaneous contraction of the isolated guinea-pig ileum. No
    effect was measured on the acetylcholine, histamine or high K+
    -induced contraction in concentrations 10-5, 10-4 and 10-3 g/ml
    (Takahashi  et al., 1986).

    Observations in humans

         Workers involved in the optimization of the production process
    and formulation of glufosinate ammonium since 1984 were exposed to
    very low levels of the substance.  These persons were subject to

    routine examinations by the manufacturer's department of industrial
    medicine in accordance with the Principles 10, 33 and 83 of the
    "Berufsgenossenschaft Chemie". Neither clinical nor laboratory
    examinations showed findings deviating from the standard values. 
    There are no reports of adverse effects on health caused by poisoning
    at the workplace or by exposure under the conditions of the
    recommended use or any published cases of accidental poisoning.  A few
    cases of suicidal poisoning were described after drinking of large
    amounts of the formulated product (200 g/l). The profile of
    intoxication observed in suicides corresponded to that observed in the
    acute toxicity studies in rodents and dogs (Ebert & Leist, 1989).

    COMMENTS

         The toxicokinetics of glufosinate-ammonium were investigated in
    rats and dogs as well as in livestock (goats and hens). The substance
    was rapidly excreted in all test species regardless of the route of
    administration.  About 80-90% of an oral dose of glufosinate-ammonium
    remained unabsorbed and was eliminated unchanged in the faeces over 48
    hours, while about 10-15% was eliminated in the urine. 

         The main metabolite of glufosinate-ammonium found in urine and in
    faeces was 3-[hydroxy(methyl)phosphinoyl] propionic acid1.  Its
    half-life was 6-7 hours  in vivo. Rats given a single oral dose of 20
    mg/kg bw 3-[hydroxy(methyl) phosphinoyl] propionic acid excreted 92%
    in the urine and 3.5% in faeces after 4 days.

         Glufosinate-ammonium competitively inhibits glutamine synthetase
    in mammals.  However, even at high (sublethal) doses, glutamate,
    ammonia and glutamine levels in brain, liver and kidney tissues were
    unaffected. No effect was seen on enzymes which have glutamate as a
    substrate nor on the metabolism of amino acids, glutathione or
    carbohydrates.  The substance did not impair the oxidative metabolism
    in mitochondria  in vitro.

         The compound showed slight to moderate acute oral toxicity in
    rats, mice and dogs; dogs were the most sensitive species.

         Short-term toxicity studies were performed in rats, mice and
    dogs. In mice, the NOAEL was 80 ppm, equal to 17 and 19 mg/kg bw/day
    in males and females respectively, based upon increased plasma
    potassium levels at the next highest dose (67 mg/kg bw/day).  In rats,
    effects on absolute kidney weights were seen at dose levels as low as
    0.52 mg/kg bw/day.  These effects on kidney weight were not found in
    the long-term bioassay in rats.  In dogs, the NOAEL was 4.5 mg/kg
    bw/day, based on decreased body weight at higher doses.  CNS
    excitation was seen only in dogs.

         When 3-[hydroxy[methyl]phosphinoyl]propionic acid, the primary
    metabolite of glufosinate-ammonium, was administered in the diet to
    rats for 28 days at concentrations of 50-5000 ppm, the NOAEL was 2500
    ppm, equal to 280 mg/kg bw/day.  An increase in liver weight was seen
    in the high-dose females.  Hepatic glutamine synthetase was unaffected
    by treatment.

                 

    1  The name 3-methylphosphinico-propionic acid was used in reports
         provided to the Meeting.

         Glufosinate-ammonium was not teratogenic in rats or rabbits. The
    NOAELs for maternal and embryo/fetal toxicity was 6.3 mg/kg bw/day in
    rabbits and 2.2 mg/kg bw/day in rats.

         Glufosinate-ammonium was not carcinogenic in long-term/
    carcinogenicity studies in rats and mice. In mice fed 0, 20, 80, or
    160 ppm (males) and 0, 20, 80, or 320 ppm (females), the NOAEL was 80
    ppm (equal to 11 mg/kg bw/day), with increased male mortality at
    higher dietary concentrations. In rats fed 0, 40, 140 or 500 ppm, the
    NOAEL was 40 ppm (equal to 2.1 mg/kg bw/day) with increased  kidney
    weight at 140 ppm.  Additional effects noted at higher doses were a
    reduction in glutathione level in liver and blood and significant
    increases in renal weight.

         In a two-generation study in rats the only effect on reproduction
    was a reduction in litter size in animals fed 360 ppm
    glufosinate-ammonium.  The NOAEL was 120 ppm, equivalent to 6 mg/kg
    bw/day.

         After reviewing the available  in vitro and  in vivo
    genotoxicity data, it was concluded that there was no evidence of
    genotoxicity.

         The ADI was based upon the NOAEL determined from the long-term
    study in rats, using a 100-fold safety factor.

    TOXICOLOGICAL EVALUATION

    Level causing no toxicological effect

         Mouse:    80 ppm in the diet, equal to 11 mg/kg bw/day
         Rat:      40 ppm in the diet, equal to 2.1 mg/kg bw/day
         Rabbit:   6.3 mg/kg bw/day
         Dog:      4.5 mg/kg bw/day

    Estimate of acceptable daily intake for man

         0-0.02 mg/kg bw

    Studies which will provide information valuable in the
    continued evaluation of the compound

    1.   Further observations in humans.

    2.   Clarification of the biological significance of the increased
         renal glutamate synthetase activity observed in rats.

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    Sachsse, K. (1986)  28-day oral toxicity (capsule) study in the dog
    with Hoe 039866 technical, 14C - Hoe 039866 with special reference
    to mode of action and target organ. Part 1. RCC project 048734. 
    Submitted to WHO by Hoechst A.G., Frankfurt-am-Main, Germany.

    Schacht, U. (1986)  Hoe 039866 - substance technical: Testing the mode
    of action by neurotransmitter receptor binding assays  in vitro.
    Hoechst Report 86.1243.  Submitted to WHO by Hoechst A.G.,
    Frankfurt-am-Main, Germany.

    Schwalbe-Fehl, M., Steinau, M., Scheinkönig, U., Kellner, H.M. &
    Eckert, H.G. (1985)  Hoe 039866-14C, metabolism and residue
    determinations in rats after single oral administration of 800 mg/kg
    body weight. CM008/85, Analytisches Laborat-orium, Hoechst
    Aktiengesellschaft.  Submitted to WHO by Hoechst A.G.,
    Frankfurt-am-Main, Germany.

    Schwalbe-Fehl, M. (1986)  Hoe 039866, ammonium-DL-homodanin-4-yl
    (methyl)-phosphinate. Summary on pharmacokinetics and metabolism in
    animal (Analytishes Laboratorium, Hoechst Aktiengesellschaft.
    Submitted to WHO by Hoechst A.G., Frankfurt-am-Main, Germany.

    Schwalbe-Fehl, M., Steinau, M., Scheinkönig, U., Kellner, H.M. &
    Eckert, H.G. (1986)  Hoe 039866-14C, metabolism and residue
    determinations in female rats after repeated oral administrations of
    10 and 100 mg/kg body weight/day, respectively. CM007/85, Analytisches
    Laboratorium, Hoechst Aktiengesellschaft.  Submitted to WHO by Hoechst
    A.G., Frankfurt-am-Main, Germany.

    Suter, P. & Sachsse, K. (1984)  28-day range finding study in rats.
    Research and Consulting Company A.G. Project 018494.  Submitted to WHO
    by Hoechst A.G., Frankfurt-am-Main, Germany.

    Suter, P. & Sachsse, K. (1986)  Combined chronic toxicity/oncogenicity
    study in the rat. Dietary administration. Research and Consulting
    Company A.G. Project 018505.  Submitted to WHO by Hoechst A.G.,
    Frankfurt-am-Main, Germany.

    Suter, P. & Sachsse, K. (1984)  13-week oral toxicity (feeding) study
    in mice. Research and Consulting Company A.G. Project 018516. 
    Submitted to WHO by Hoechst A.G., Frankfurt-am-Main, Germany.

    Suter, P. & Sachsse, K. (1986)  2-year oncogenicity study in mice.
    Dietary administration. Research and consulting Company A.G. Project
    018527.  Submitted to WHO by Hoechst A.G., Frankfurt-am-Main, Germany.

    Takahashi, H., Tsuda, S., Ikeda, T., Tanaka, J., Elbino, K. & Shirasu,
    Y. (1986) Hoe 039866 OH ZC97 0003 - general pharmacology study. The
    Institute of Environmental Toxicology.  Submitted to WHO by Hoechst
    A.G., Frankfurt-am-Main, Germany.

    Til, H.P. & de Groot, A.P. (1982)  Sub-chronic (90-day) toxicity study
    in dogs. CIVO TNO V82.318/201720.  Submitted to WHO by Hoechst A.G.,
    Frankfurt-am-Main, Germany.

    Wink, O., Haberkorn, B., Künzler, K. & Kellner, H.M. (1986)  Hoe
    039866-14C, metabolism in male and female rats after a single oral
    administration of 2 mg/kg body weight each. CMO82/85I, Analytisches
    Laboratorium, Hoechst Aktiengesellschaft.  Submitted to WHO by Hoechst
    A.G., Frankfurt-am-Main, Germany.

    Wink, O., Haberkorn, B., Künzler, K. & Kellner, H.M. (1986)  Hoe
    039866-14C, metabolism in male and female rats after repeated oral
    administrations of 2 mg/kg body weight each on 15 consecutive days.
    CMO82/85II, Analytisches Laboratorium, Hoechst Aktiengesellschaft. 
    Submitted to WHO by Hoechst A.G., Frankfurt-am-Main, Germany.

    Wink, O., Dorn, E., Künzler, K., Haberkorn, B. & Kellner, H.M. (1986) 
    Hoe 039866-14C, metabolism in male and female rats after a single
    administration of 30 mg/kg body weight each. Doc. A33895 CMO83/85,
    Analytisches Laboratorium, Hoechst Aktiengesellschaft.  Submitted to
    WHO by Hoechst A.G., Frankfurt-am-Main, Germany.


    See Also:
       Toxicological Abbreviations
       Glufosinate-ammonium (JMPR Evaluations 1999 Part II Toxicological)