Steroidogenesis in Rat Leydig Cells: Effect of Gonadotropins on the Activity of 5-Ane and 5-Ene 3α- and 3β-Hydroxysteroid Dehydrogenases during Sexual Maturation*

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Abstract
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 [chorionic gonadotropin] for 5 days starting at 20 days of age and the testicular 12,000 .times. g supernatants were assayed for steroid oxidoreductase activities. Marked increases (up to 8-fold) were noted in the rate of oxidation of the 3.beta.-hydroxyl of 3.beta.-hydroxy-5.beta.-androstan-17-one, 3.beta.-hydroxy-5.alpha.-androstan-17-one, 5.alpha.-androstane-3.beta.,17.beta.-diol, dehydroepiandrosterone and pregnenolone, and in the 3-keto reduction of 17.beta.-hydroxy-5.alpha.-androstan-3-one, 17.beta.-hydroxy-5.beta.-androstan-3-one, 5.beta.-androstane-3,17-dione and 5.alpha.-androstane-3,17-dione. The hormone response required a certain amount of time as no response was detected until 72 h after the 1st injection. As little as 1 IU hCG/injection resulted in significant increases in 3.beta.-oxidoreductase (3.beta.-HSD) activities. FSH [follicle stimulating hormone] and TSH [thyroid stimulating hormone] gave no significant increases and 25 .mu.g NIH-LH-S18 [National Institute of Health Luteinizing Hormone] resulted in increases only when the hormone was suspended in a sesame oil-beeswax mixture. Hormone treatments did not result in increased 5-ane-3.alpha.-HSD activities. Rats receiving chronic human CG treatment starting at 66 days of age showed less marked increases in 5-ane-3.beta.-HSD activities than the younger rats and no significant enhancement in 5-ene-3.beta.-HSD. 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-3.beta.-oxidoreductases.