Formation of 5,16-androstadien-3 beta-ol from pregnenolone in human testicular microsomes.

A microsomal fraction of testicular tissue from a patient with prostatic carcinoma was incubated with [4-14C]pregnenolone in the presence of an NADPH-generating system for different periods of time. The metabolites were separated by Sephadex LH-20 column chromatography and then identified by thin-layer chromatography, radio-gas chromatography, and crystallization studies. Pregnenolone was converted to a major metabolite, 5-androstene-3 beta,17 beta-diol via 17-hydroxypregnenolone and then dehydroepiandrosterone. Another major metabolite was 5,16-androstadien-3 beta-ol, which increased with the time of incubation and accumulated in the incubation medium. After 120 min of incubation, 34.6% of the precursor was converted to 5-androstene-3 beta,17 beta-diol and 15.1% to 5,16-androstadien-3 beta-ol. In addition to the above-mentioned steroids, 16 alpha-hydroxypregnenolone, 5-pregnene-3 beta,20 alpha-diol, and 5-androstene-3 beta,17 alpha-diol were identified as minor metabolites of pregnenolone. From these results it was concluded that human testicular microsomes possess enzymic activities for the synthesis of 5,16-androstadien-3 beta-ol, as well as androgens from pregnenolone.