Steroidogenesis in rat leydig cells: changes in activity of 5-ane and 5-ene 3beta-hydroxysteroid dehydrogenases...

The activities of hydroxysteroid dehydrogenases of 5-ane and 5-ene steroids were examined in interstitial tissue from testes of rats at different ages. The enzyme reactions were localized in the Leydig cell cytoplasm of isolated cells and in frozen tissue slices. Relative reaction velocites of the NAD-linked hydroxysteroid dehydrogenases were obtained spectrophotometrically with 17 steroid substrates using the 12,000 X g supernatant of isolated interstitial cells from 28-29 day old rats; the rate of 3(alpha,beta) dehydrogenation of 5-ane-3beta steroids was markedly (10 to 20X) higher than that of 5-ene-3beta steroids and 5-ane-3alpha steroids. The hydroxysteroid dehydrogenase activities of testes from 124 rats between the ages of 15 and 138 days were determined using as substrates, 3beta-hydroxy-5beta-androstan-17-one, 3beta-hydroxy-5alpha-androstan-17-one, 3beta,17beta-dihydroxy-5alpha-androstane, dehydroepiandrosterone and pregnenolone. Between the ages of 15 and 32 or 34 days the gonads grow in size more rapidly than the body and the 5-ane-3beta-hydroxysteroid dehydrogenase activities show very marked increases; changes in the 5-ene-3beta-hydroxysteroid dehydrogenases are much less pronounced, so that at 34 days the activity of 3beta-hydroxy-5beta-androstan-17-one dehydrogenase is approximately 20 X that of dehydroepiandrosterone dehydrogenase. After 34 days, the 5-ane-3beta-hydroxysteroid dehydrogenase activities decline. It is suggested that during sexual maturation the testicular biosynthesis of active 5-ane androgens may proceed via 5-ane precursors with the help of age-dependent 5-ane-3beta-hydroxysteroid dehydrogenases.