Steroidogenesis in Rat Leydig Cells: Changes in Activity of 5-ane and 5-ene 3β-Hydroxysteroid Dehydrogenases During Sexual Maturation

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 velocities of the NADlinked hydroxysteroid dehydrogenases were obtained spectrophotometrically with 17 steroid substrates using the 12,000 ì g supernatant of isolated interstitial cells from 28–29 clay old rats; the rate of 3(α,β) dehydrogenation of 5-ane-3β steroids was markedly (10 to 20ì) higher than that of 5-ene-3β steroids and 5-ane-3α steroids.

The hydroxysteroid dehydrogenase activities of testes from 124 rats between the ages of 15 and 138 days were determined using as substrates, 3β-hydroxy- 5β-androstan-17-one, 3β-hydroxy-5a-androstan- 17-one, 3β,17β-dihydroxy-5α-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-3β- hydroxysteroid dehydrogenase activities show very marked increases; changes in the 5-ene-3β-hydroxy-steroid dehydrogenases are much less pronounced, so that at 34 days the activity of 3β-hydroxy-5β- androstan-17-one dehydrogenase is approximately 20 ì thatofdehydroepiandrosterone dehydrogenase. After 34 days, the 5-ane-3βydroxysteroid 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-3β-hydroxysteroid dehydrogenases. (Endocrinology98: 505, 1976)