Effect of Zinc on Androgen Metabolism In the Rat Ventral Prostate

Abstract

The in vitro effect of zinc on the metabolism of androgen was examined to identify the role of zinc on the regulation of dihydrotestosterone level in the prostate. The activities of 5 a -reductase and 3 a -hydroxysteroid oxidoreductase were assayed in the homogenate of the rat ventral prostate with eH)-testosterone or (3H)-dihydrotestosterone as a substrate in the presence of 5 x 10-4 M NADPH. The zinc content of normal rat ventral prostate measured by atomic absorption spectroscopy was 29.92 ± 5.56 p g per gm tissue of wet weight. The Km and Vmax values of 5-reductase were 353.5 ± 32.3 nM and 41.8 + 1.1 pmole/30 min/mg protein respectively and of 3 a -hydroxysteroid oxidoreductase were 1477.2 ± 177.4 nM and 823.2 ± 81. 7 pmole/30 min/mg protein. Zinc inhibited both enzymes in a non-competitive manner respecting to the substrate. The half inhibition concentration of zinc on 5 a -reductase and 3 a -hydroxy-steroid oxidoreductase were 18.3 ± 5.2 and 97.4± 33.0 fl M respectively. From this experiment it was suggested that zinc might play an important role on the regulation of dihydro-testosterone level in the prostate by influencing the activities of 5 a -reductase and 3 a -hydroxysteroid oxidoreductase.