Collaborative work to evaluate toxicity on male reproductive organs by repeated dose studies in rats 13). Effects of a single oral dose of cyclophosphamide.

As part of a collaborative effort to evaluate whether effects on male reproductive organs of chemicals can be detected within two-week in toxicity studies, eight-week-old male Sprague-Dawley rats were given a single oral administration of 100 mg/kg of Cyclophosphamide (Cp), and sacrificed at 1, 3, 7 and 14 days thereafter. The numbers of seminiferous epithelial cells were counted in the seminiferous tubules of stages II-III, V, VII and XII of the spermatogenic cycle. Animals showed decreased spermatogonia at Day 3, decreased spermatogonia and preleptotene spermatocytes at Day 7, and decreased spermatogonia and zygotene spermatocytes at Day 14. We also detected decrease of zygotene spermatocytes on careful routine/traditional histopathological examination at Day 14. These results suggest that the testicular toxicity of Cp can be detected within two weeks after treatment with a sufficient dose in rats.