Characterization and endocrine regulation of the cytochrome P-450 dependent microsomal hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol in the rat ventral prostate.

Of 11 structurally related steroids, 5 alpha-androstane-3 beta,17 beta-diol was the one most efficiently hydroxylated to polar metabolites by microsomes isolated from the rat ventral prostate. The metabolites were identified by gas chromatography-mass spectrometry as 6 alpha-,7 alpha-, and presumably 6 beta-hydroxylated 5 alpha-androstane-3 beta,17 beta-diol. The hydroxylated metabolites were separated and quantitated by high performance liquid chromatography using an aminopropylsilane hypersil column. Maximum velocity (V max) values of 0.36, 0.12, and 0.044 nmol/min X mg of microsomal protein were determined for the 6 alpha-,7 alpha-, and 6 beta-hydroxylase activities, respectively, with an apparent Michaelis-Menten constant (Km) of 30 microM for all hydroxylases. Hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol in prostatic microsomes was NADPH dependent and was inhibited by several cytochrome P-450 inhibitors in vitro and by antibodies against rat liver NADPH-cytochrome P-450 reductase. The enzyme activities were stimulated by treatment of the rats with phenobarbital, beta-naphthoflavone, 5 alpha-androstane-3 beta,17 beta-diol,5 alpha-dihydrotestosterone, and methyltrienolone, whereas the activities were suppressed by ovine PRL, human GH, estradiol benzoate, cholesterol, andrenalectomy , hypophysectomy, and castration. It is concluded that the prostatic 5 alpha-androstane-3 beta,17 beta-diol hydroxylase activities represent a constitutive cytochrome P-450 form in the rat ventral prostate with a high steroid substrate specificity. Endocrine factors are involved in the regulation of the activity of the enzyme. The ratio between the three hydroxylated metabolites was constant in almost all experiments suggesting that only one cytochrome P-450 species was involved in the hydroxylation.