Microsomal effects of cyproterone acetate and flutamide in rat testis.

1. Effects of two doses of cyproterone acetate (CA) and flutamide (FLU) (50 and 100 mg/kg/3 days) on the testicular steroidogenesis in male rats have been investigated, by measuring the content of cytochrome P-450, cytochrome b5 and cytochrome c reductase activity in the microsomal fraction. 2. CA provoked a significant decrease in cytochrome P-450 content while FLU induced an increase with the lowest dose but a significant decrease after administration of 100 mg/kg. 3. On the other hand, in all cases the cytochrome b5 and cytochrome c reductase activity remained unchanged. 4. The plasma levels of LH and testosterone were measured after CA and FLU injection (50 and 100 mg/kg/3 days). 5. CA administration provoked a reduction in blood levels of these hormones while FLU induced a significant increase in both. 6. These data suggested that CA and FLU modified the cytochrome P-450 in rat testes by an indirect mechanism, probably through the modification of LH plasma levels.