SECONDARY ALCOHOL-DEHYDROGENASE AS A MARKER OF THE CONVERSION BETWEENPROGESTAGENS AND ANDROGENS IN THE RAT TESTIS

Supraphysiological doses of LHRH-Analogue blocked the C-21 to C-19 ste roid conversion in the mature Wistar rats testis. It was associated wi th inhibition of the NAD-dependent secondary alcohol-dehydrogenase (A- D II) histochemical reaction in the Leydig cells. Under this condition the treated group exhibited lower testis, seminal vesicle and prostat e weights, intratesticular (IT) and plasmatic (PL) increased progester one (P-4) and decreased testosterone (T) concentrations. We also obser ved a decrease in the TT androstenedione (Delta(4)) concentration with out pregnenolone (P-5) change. All these data confirm a chemical castr ation pointing to a blockade at the level of the P-450C21scc (17 alpha -hydoxylase/17-20 desmolase) enzyme complex. After hCG administration there is no difference in sexual gland weights, while steroid's biosyn thesis are stimulated and all IT and PL steroid concentrations increas e. A-D II showed a lower optical density in the LHRH-A treated groups and no differences in the hCG rats. The hydroxylase or lyase activity of the P-450C21scc may change under certain hormonal conditions as occ urs in adrenarche, probably due to conformational changes in the activ e site of the enzyme system since it is encoded by only one gene. We s uppose that the secondary alcohol itself and not the coenzyme reacts w ith the enzyme active site inhibited by the LHRH-A, since the NAD depe ndent 3 beta,hydroxysteroid-dehydrogenase (3 beta HOST-D) is affected in the opposite sense. This study shows A-D II reaction as a marker of the mediated P-450C21scc enzyme complex activity in the rat testis Le ydig cells.