Effects of Finasteride on the Rat Ventral Prostate

Abstract

ABSTRACT: The objectives of this study were to compare changes in the ventral prostate (VP) of young adult Sprague Dawley rats after 28 days of treatment with finasteride (F), a potent 5α‐reductase inhibitor, with those caused by castration (Cx). VP concentrations of DHT were reduced to 20.2% and 6.6% of controls (1,947 ± 207 pg/VP, mean ± SE) by F (5 or 20 mg/kg/day) and to 2.6% of controls by Cx. VP weights were reduced 49% and 54% by F and 88% by Cx. DNA/VP fell 25% and 15% with F treatment and 72% after Cx, whereas RNA and protein/VP were reduced 37–51% by F and 91–93% by Cx. The RNA/DNA and the protein/DNA ratios fell to 30–36% of controls after F treatment and to 70% of controls after Cx. The mRNA concentrations of the C3subunit of prostatein 28S ribosomal RNA fell after treatment with F (5 mg/kg/day) and after Cx, whereas the mRNA for TRPM‐2, an androgen‐suppressed protein associated with apoptosis, was increased only after castration. To examine further the effects of F on the rate of DNA synthesis, 7‐day regressed adult rats were treated for 3 days with testosterone propionate ± F, and incorporation of 3H‐thymidine in minced ventral prostates was determined. F inhibited 3H‐thymidine incorporation. We conclude that Cx causes a greater reduction in cell number/VP and a greater reduction in RNA and protein/cell than F and that the differences between F treatment and castration probably result from differences in prostatic concentrations of T. However, we cannot exclude the possibility that small differences in DHT contribute to these differences.