Collaborative work to evaluate toxicity on male reproductive organs by repeated dose studies in rats 26). Detection of 1,3-dinitrobenzene-induced histopathological changes in testes and epididymides of rats with 2-week daily repeated dosing.

As part of a collaborative work, male rats were administered 1,3-dinitrobenzene (1,3-DNB) daily at 0, 25 and 50 mg/kg/day from the age of 6 weeks for 4 weeks (4-week exp.), or at 25, 50 and 75 mg/kg/day from the age of 8 weeks for 2 weeks (2-week exp.). After the end of each administration period, all survivors were sacrificed, and their testes and epididymides were removed, weighed and examined histopathologically. The following results were obtained. In the 4-week exp.: At 50 mg/kg/day, the weights of testes and epididymides showed decrease with macroscopic atrophy. The testicular spermatogenic epithelium showed decrease in the number of sperm-spermatocytes, degeneration/necrosis, giant cell formation and vacuolation, reduction in sperm counts also being evident in the ducts of the epididymides. In the 2-week exp.: At 50 and 75 mg/kg/day, the weights of testes and/or epididymides showed decrease with macroscopic atrophy. Several histopathological changes in the testes and epididymides were essentially the same changes as in the group given 50 mg/kg/day in the 4-week exp., with a clear relation. These results indicate that a 2-week administration period is sufficient to detect testicular and epididymal histopathological changes induced by 1,3-dinitrobenzene in male rats.