Effect of sodium molybdate on the binding of androgen-receptor complexes to germ cell and sertoli cell chromatin

Abstract

This study explores the effect of molybdate on androgen receptors in relation to chromatin binding. Two fractions of testicular and prostatic cytosol were obtained by ammonium sulfate precipitation at 15–37% (I) and 37–47% (II) saturation. Both fractions from either tissue exhibited specific binding of [ 3H]-androgens which was thermolabile. With the exception of testicular fraction II, all fractions bound to Sertoli cell and germ cell chromatin. Prostatic [ 3H]-androgen-receptor complexes isolated from cytosols in the presence of 10 mM sodium molybdate showed a decreased ability (only 20–40%) to bind to either Sertoli cell or germ cell chromatin. Similarly, testicular [ 3H]-androgen-receptor complexes isolated in the presence of molybdate bound less well (60–70%) to Sertoli cell chromatin. On the other hand, inclusion of molybdate subsequent to ammonium sulfate precipitation did not significantly alter the binding ability of the receptor complexes to either chromatin. Also, the presence of molybdate during the receptor-chromatin interaction did not significantly decrease the ability of either prostatic or testicular androgen-receptor complexes to bind to Sertoli cell chromatin. These results indicate that the addition of molybdate prior to ammonium sulfate precipitation may impede the activation of androgen-receptor complexes by salt, resulting in a decreased ability of the steroid-receptor complexes to bind to chromatin acceptor sites. The data also indicate that molybdate exerts its inhibitory effect directly on the nonactivated receptor complexes and not on the chromatin acceptor sites.