LITHOL RUBINE BK EXPLANATION Lithol rubine BK was considered at the twenty-first and twenty-sixth meetings of the Committee (Annex 1, references 44 and 59), but insufficient data were available for evaluation for an ADI. Since that time further data have become available and are summarized below. BIOLOGICAL DATA Biochemical aspects No information available. Toxicological studies Acute studies No information available. Short-term studies No information available. Long-term studies Mice Groups of 60 male and 60 female Charles River CD1 mice were fed diets containing 0.05, 1.0, or 5.0% lithol rubine BK for 104 weeks; two groups of 60 animals of each sex were used as controls. Individual body weights were recorded weekly for the first 14 weeks, biweekly during the next 12 weeks, and monthly thereafter. Haematological examinations (haemoglobin, haematocrit, RBCs, total and differential leucocyte counts, and reticulocyte counts) were carried out on 10 mice/sex/group at 3, 6, 12, and 18 months. At termination of the study, all animals were necropsied and the weights of the brain, kidneys, liver, and spleen were recorded. Complete histopathological examination was carried out on the control and high-dose groups only. No significant differences were observed in food consumption, body-weight gain, or haematological parameters except for a depressed reticulocyte count in the high-dose groups relative to controls after 18 months, although the counts were within the expected range for mice of that age. Beginning at week 64, there was a treatment-related increase in mortality in males, and survival was significantly reduced in the 5% dose group at 91 and 104 weeks; increased mortality was not observed in females. No toxicologically-significant dose-related differences in organ weights or gross morphology were observed. Histopathological examination of animals dying on test and of animals examined at termination revealed a variety of degenerative, inflammatory, proliferative, or neoplastic lesions commonly associated with aging mice that occurred with similar frequency or sporadic distribution in controls and high-dose groups. Exceptions were degenerative renal changes, which occurred with higher incidence among treated males dying on test or terminally sacrificed, and alveolar adenomas, which were the most common tumours occurring in the study. Statistically- significant increases in the unadjusted incidence of alveolar adenomas were seen in high-dose males, but these were considered of dubious toxicological significance because of unequal sampling of the low- and mid-dose groups and because of earlier diagnosis associated with the increased mortality in the high-dose group. No significant treatment-related increases were seen in tumours or non-neoplastic lesions at other sites, the occurrence of which were considered incidental or common for aged mice (IRDC, 1981a). Rats In a long-term study with an in utero phase, lithol rubine BK was administered to Charles River CD rats at dietary concentrations of 0, 0.05, 0.3, or 2%. In the in utero segment of the study, 60 rats of each sex were assigned to each treatment group and then mated after receiving the appropriate diet for 60 days. A minimum of 35 litters per dosage level was used to select 70 rats of each sex per group for the long-term segment of the study. In the reproductive phase, observations were made of the fertility index, gestation anomalies, and effects on parturition and lactation; indices for live births and survival to weaning were calculated. In the long-term phase, the pups were weaned onto their respective diets at 21 days and maintained on these diets throughout the remainder of the experiment. Individual body weights and food consumption measurements were recorded weekly throughout the in utero phase and the first 14 weeks of the long-term phase, biweekly for the next 12 weeks, and monthly thereafter. Ophthalmoscopic examinations, haematology (haemoglobin, haematocrit, total and differential leucocyte counts, RBCs, and reticulocyte counts), biochemical examinations (fasting glucose, BUN, SGOT, SGPT, serum alkaline phosphatase, total serum protein, and creatinine) and urinalysis (colour, pH, SG, qualitative tests for protein, glucose, bilirubin, ketones, occult blood, and microscopy on the sediment) were performed on 10 rats/sex/group at 3, 6, 12, 18, and 21 months (males) and at 3, 6, 12, 18, and 24 months (females) in the long-term phase. Additional haemato logical (5 rats/sex/group), virological (2 rats/sex/ group), and microbiological (3 rats) evaluations were conducted at 20 months. An interim sacrifice and necropsy of 10 rats/sex/group was conducted after 12 months of treatment. For animals killed at the interim or terminal sacrifices, organ weights were recorded of the brain, kidney, liver, spleen, testes, thyroid, heart, adrenals, uterus, and ovaries. Complete histopathological examination was carried out on the control and high-dose groups only. For the in utero phase, no compound-related effects were seen on body weights, food consumption, ophthalmoscopic examination, fertility, or gestation and lactation indices. In the long-term phase, mean food consumption values were similar for control and treated rats, but there was a treatment-related depression in body-weight gain, most marked in the high-dose group. Males showed a larger decrement of body-weight gain than females in the same dose group, the deficit compared to controls reaching about 19% for high-dose males by week 91 of the study. There was an accelerated mortality rate in male rats in the high-dose group and, for males, the study was terminated at week 95 when there were only 9 survivors in the high-dose group compared with 17 and 29 in the two control groups. No changes considered to be related to treatment were seen in the haematological and clinical biochemical examinations and, apart from the colour of the urine, no differences attributable to treatment were observed in urinalysis values. At 20 months, the additional haematological investigation revealed no treatment-related effect, but one low-dose male and one high-dose male had markedly elevated leucocyte counts. Virological investigations showed that titres for the viruses PVM and KRV were higher than expected for rats of that age, and microbiological examination of lung and tracheal samples from three rats revealed infection with Mycoplasma pulmonis; the most prominent organism in the tissues of these animals was Pseudomonas. No compound-related macroscopic changes were detected in rats which were sacrificed at 12 months or terminally. There were no statistically-significant variations in mean organ weights at the 12-month interim sacrifice, and subsequent statistically-significant variations in the high-dose males were related to the decrement in mean body weight. Histopathological examinations revealed a higher incidence of chronic nephritis, renal tubular epithelial hyperplasia, myocardial fibrosis, reticular hyperplasia, and pigment deposition in the spleeen than in the controls. Atrophy/degeneration of testicular tubules in high-dose males that died on study from 12 months to termination was also higher than in the controls. These changes are common in aging rats and no specific compound effect was identified other than an acceleration of these changes. There was no significant increase in incidence of the above lesions at termination. For all malignant tumours in the males, the Z statistic was significant at the 0.01 level in the Kruskal-Wallis test for adjusted trend, but it was claimed that this single value was not toxicologically significant because of the small number of tumours present (unadjusted incidence was 4% in the controls and 9% in the high-dose group). There was an unusually high incidence of pituitary adenomas in one control group of males; the incidence in the high-dose group was not significantly increased over either control group. The unadjusted incidence of Leydig cell adenomas in males was 2% in controls and 6% in high-dose animals, not significant at the 0.05 level, but tests for unadjusted trend and homogeneity of life table curves were significant at the 0.01 level. However, they were of doubtful toxicological significance because of the small number of tumours involved (IRDC, 1981b). Observations in man No information available. Comments In the long-term mouse study, there was a dose-related increase in mortality and renal pathology, but detailed histopathology was not conducted on the low- and intermediate-dose groups. The long-term study in rats was complicated by high mortality rates, which led to premature termination of the study for males. In addition, only limited histopathological examinations were conducted. In view of these limitations, it was not possible to determine an unequivocal no-effect level in either study. Therefore, an ADI could not be established. EVALUATION Estimate of acceptable daily intake for man No ADI allocated. Further work or information Required for re-evaluation for an ADI 1. Results of a complete histopathological examination of all dose groups in the long-term mouse study. 2. Results of a new long-term study in rats. 3. An adequate reproduction/teratology study. REFERENCES IRDC (1981a). D&C Red No. 6. Long-term feeding study in mice. Unpublished report No. 355-012 from International Research and Development Corporation. Submitted to WHO by the Public Health Administration, Leidschendam, The Netherlands. IRDC (1981b). D&C Red No. 6. Long-term feeding study in rats exposed in utero. Unpublished report No. 355-014 from International Research and Development Corporation. Submitted to WHO by the Public Health Administration, Leidschendam, The Netherlands.
See Also: Toxicological Abbreviations LITHOL RUBINE BK (JECFA Evaluation)