5alfa-Reductase and glucocorticoid action in toad testes

REGUEIRA ELEONORA; SCAIA MARÍA FLORENCIA; CEBALLOS NORA RAQUEL

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica.; 2007

SAIB

In the toad, breeding levels of corticosterone (CORT) decrease testosterone (T) synthesis by inhibiting the enzyme Cyp450c17. The effect of non-breeding levels of CORT is blocked by the activity of 11beta-hydroxysteroid dehydrogenase (11betaHSD), enzyme located in Leydig but not in Sertoli cells. Thus, that enzyme cannot counteract the effect of CORT on Sertoli cells, which express glucocorticoid receptors (GR) and 5alpha-reductase (5alphaRed). As in Sertoli cells 5alphaRed could be involved in the regulation of CORT access to GR, its rol in Bufo arenarum testes was studied by analyzing spermiation and T production after 24-hr incubation under different conditions. T synthesis was measured by RIA and hCG-induced spermiation by counting spermatozoa in incubation media. CORT decreases T secretion, the effect being abolished by RU486 but enhanced by glycyrrhetinic acid (GA), signifying that 11betaHSD modulates CORT effect in Leydig cells. After 24-hr incubation, hCG-induced spermiation decreases but in the presence of physiological concentrations of CORT (15 or 150 nM), it was similar to time 0 values. Finasteride decreases CORT action, suggesting that CORT effect in spermiation is mediated by its conversion in 5alpha- dihydrocorticosterone (5alphaDHB). As with T synthesis, RU486 completely abolished the effect of 5alphaDHB suggesting that its action on spermiation is due to the interaction with GR in Sertoli cells.