Testicular steroidogenesis in the camel (Camelus dromedarius) during the mating and the nonmating seasons

Enzyme reactions in the camel testis involved in androgen synthesis were studied to determine the factors which account for the low testosterone production during the non-mating season (NMS). Testes excised during the NMS were found to have a relatively high activity of the 3 beta-hydroxysteroid dehydrogenase systems of pregnenolone, 17 alpha-hydroxypregnenolone, and dehydroepiandrosterone, but the 4-ene-17 alpha-hydroxylase and 4-ene-17,20-lyase systems were apparently less active than the 5-ene-17 alpha-hydroxylase and 5-ene-17,20-lyase. On the other hand, testes excised during the mating season (MS) were found to have a relatively high activity of 4-ene-17 alpha-hydroxylase, 4-ene-lyase, and 17 beta-hydroxysteroid oxidoreductase. The 19-hydroxylation and aromatizing activities for testosterone and androstenedione were not detected in testes excised in either season. It is proposed that during the NMS the predominant route of testosterone biosynthesis is pregnenolone leads to 17 alpha-hydroxypregnenolone leads to dehydroepiandrosterone leads to androst-5-en-3 beta, 17 beta-diol leads to testosterone.