SHORT-TERM TOXICITY OF PHOTOMIREX IN THE RAT

When photomirex (8-monohydromirex) was fed to rats at dietary levels of 0, 0.5, 5.0, 50, or 500 ppm, all 10 animals receiving the highest dose levels died within 7 days, and two of 10 animals in the 50-ppm group died after 24 days. All other animals (10 per group) survived until the experiment was terminated at 28 days. Animals receiving 50 ppm showed decreased body weight gain and food consumption. Liver hypertrophy and increased microsomal enzyme activity (aniline hydroxylase) were observed in groups of animals receiving 5.0 ppm and greater. Serum sorbitol dehydrogenase activity was increased in animals receiving 5.0 ppm and greater. Photomirex accumulated in all tissues examined, with fat and liver having the highest residues. Histological alterations were observed in the liver at 0.5 ppm and consisted of mild midzonal cytoplasmic enlargement. At a level of 5 ppm, the midzonal cytoplasmic enlargement was more pronounced and was accompanied by mild anisokaryosis and nuclear hyperchromicity. At the highest dose, these alterations were accompanied by perivenous fatty infiltration. Lesions of the thyroid were observed in the group of animals receiving 50 ppm (6.61 mg/kg/day) and consisted of a generalized reduction in follicle size and colloid density. Animals which died showed pronounced thyroid follicular atrophy accompanied by severe colloid depletion and epithelial exfoliation. Animals receiving 50 ppm also had lesions in the testes consisting of a mild to marked reduction in spermatogonia and complete cessation of spermatogenesis. © 1979.