Time dependence for the protective effect of androgen from procarbazine-induced damage to rat spermatogenesis.

The protective effects of androgen pretreatment on the procarbazine-induced killing of spermatogonial stem cells in Wistar rats have been investigated. Using testosterone-filled Silastic implants (200 mm2) the degree of protection from four weekly doses of procarbazine (100 mg/kg) was found to be dependent upon the androgen pretreatment time interval as assessed by quantitative histology. No protective effect was seen until rats had received 4 wk of pretreatment with androgen, whereafter protection increased to a maximum (about 20 to 30% of tubule cross-sections exhibiting recovery) after 8 to 12 wk of pretreatment. In contrast, the same level of maximal protection could be obtained by 6 wk of pretreatment using testosterone enanthate, suggesting that differences in protection may be achieved using different modes of androgen administration.