Steroidogenesis in rat Leydig cells: effect of gonadotropins on the activity of 5-ane and 5-ene 3alpha- and 3beta-hydroxysteroid dehydrogenases during sexual maturation.

The in vivo influence of gonadotropins on the activities of oxidoreductases of androst-5-ane and androst-5-ene steroids and pregnenolone was examined in testes from young rats. Animals were given daily injections of human CG for 5 days starting at 20 days of age and the testicular 12,000 X g supernatants were assayed for steroid oxidoreductase activities. Marked increases (up to 8-fold) were noted in the rate of oxidation of the 3beta-hydroxyl of 3beta-hydroxy-5beta-androstan-17-one, 3 beta-hydroxy-5alpha-androstan-17-one, 5alpha-androstane-3beta,17beta-diol, dehydroepiandrosterone, and pregnenolone, and in the 3-keto reduction of 17beta-hydroxy-5alpha-androstan-3-one, 17beta-hydroxy-5beta-androstan-3-one, 5beta-androstane-3,17-dione, and 5alpha-androstane-3,17-dione. The hormone response required a certain amount of time as no response was detected until 72 h after the first injection. As little as 1 IU hCG/injection resulted in significant increases in 3beta-oxidoreductase (3beta-HSD) activities. FSH and TSH gave no significant increases and 25 microgram NIH-LH-S18 resulted in increases only when the hormone was suspended in a sesame oil-beeswax mixture. Hormone treatments did not result in increased 5-ane-3alpha-HSD activities. Rats receiving chronic human CG treatment starting at 66 days of age showed less marked increases in 5-ane-3beta-HSD activities than the younger rats and no significant enhancement in 5-ene-3beta-HSDs. It is suggested that during sexual maturation the testicular biosynthesis of active 5-ane androgen(s) proceeds via 5-ane precursors with the help of age and gonadotropin-dependent 5-ane 3beta-oxidoreductase.