5 alpha-reductase activity in epithelium and stroma of prostates from intact and castrated dogs treated with androstenedione, the aromatase inhibitor 1-methyl-1,4-androstadiene-3,17-dione, and cyproterone acetate.

In addition to the histology of epithelial and stromal elements of prostates from intact dogs (group 0) and castrated dogs (group I), the latter of which were treated with androstenedione (group II), androstenedione plus the aromatase inhibitor 1-methyl-1,4-androstadiene-3,17-dione (group III), or androstenedione plus aromatase inhibitor and cyproterone acetate (group IV) (Habenicht and El Etreby: The Prostate 11:133-143, 1987) it was of interest to study the influence of such in vivo treatment on the prostatic 5 alpha-reductase, which is responsible for the cellular conversion of testosterone to 5 alpha-dihydrotestosterone. Michaelis constants (KM) and maximal activities (Vmax) of 5 alpha-reductase were determined under optimized incubation conditions in mechanically separated epithelium and stroma. The metabolites were separated by high-performance liquid chromatography and determined radiometrically. The main results were: 1) The mean KM (nM +/- SEM) was significantly (P less than .001) higher in epithelium (892 +/- 132) than stroma (70 +/- 11). The same was true concerning the Vmax (pmol.mg protein-1.h-1 +/- SEM) in epithelium (54.6 +/- 5.8) as compared to stroma (13.0 +/- 2.0). 2) No specific in vivo or in vitro effect of the aromatase inhibitor on the KM and Vmax data was found. 3) In prostates of intact dogs and dogs of group II the proportion of epithelial 5 alpha-reductase exceeded distinctly that of stromal 5 alpha-reductase. 4) In groups I, III, and IV the proportion of epithelial 5 alpha-reductase was rather low. These data were discussed in the light of the histological findings.