title: Role of nicotinamide adenine dinucleotide in ethanol-induced depressions in testicular steroidogenesis.
abstract: It is rapidly becoming accepted, without direct evidence, that a change in the NAD+/NADH ratio in the testes produced by the metabolism of ethanol is the principal mechanism involved in its now well-established effects on testicular steroidogenesis. The purposes of the present studies were 2-fold: (1) to examine whether, in fact, in vivo or in vitro ethanol exposure alters the NAD+/NADH ratio in the testes; and (2) to examine the validity of previous reports in which it was found that NAD+ prevented the effects of ethanol on testicular steroidogenesis under in vitro conditions. With regard to the first objective, we found that a large dose of ethanol (2.5 g/kg) markedly reduced gonadotropin-stimulated testicular steroidogenesis in vivo in the male rat, but it did not alter the NAD+ and NADH concentrations in the testes. Similarly, extremely high ethanol concentrations (200 mM) substantially suppressed hMG-stimulated testosterone biosynthesis in in vitro Leydig cell preparations but no change in NAD+ concentration occurred; NADH levels were very low in the Leydig cell preparations (less than 2% of NAD+ levels), but did not appear to change as a function of ethanol exposure. Finally, in contrast to previously published results, we found that NAD+ (1 mM) did not prevent the in vitro effects of ethanol on cAMP-stimulated testicular steroidogenesis. Consequently, our results fail to support the hypothesis that acute in vivo or in vitro ethanol administration inhibits the biosynthesis of testosterone by altering the NAD+/NADH ratio in the testes.
mesh_terms: D000079:Acetaldehyde / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D006062:Gonadotropins / Q000494:pharmacology; D008297:Male; D009243:NAD / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis*
chemical_list: D006062:Gonadotropins; D009243:NAD; D000431:Ethanol; D013739:Testosterone; D000242:Cyclic AMP; D000079:Acetaldehyde