Testicular steroid sulfotransferases: comparison to liver and adrenal steroid sulfotransferases of the mature rat.

Steroid sulfotransferase activity was investigated in cytosol fractions of whole testes, isolated seminiferous tubules, isolated interstitial tissue, livers, and adrenal glands of mature male rats. Enzyme activity was measured by incubating cytosol fractions with 3H-labeled pregnenolone, dehydroepiandrosterone, testosterone, or estradiol and the active sulfate donor 3'-phosphoadenosine-5'-phosphosulfate. Testicular steroid sulfotransferase activity was found in seminiferous tubules. 3 beta-Hydroxysteroid sulfotransferase activity of seminiferous tubules exhibited a pH optimum of 10 in contrast to a pH optimum of 5 reported for cytosol fractions of rat liver. Marked differences in substrate specificity were demonstrated in the three tissues. The preferred substrate for the 3 beta-hydroxysteroid sulfotransferase in seminiferous tubules was pregnenolone, and in liver it was dehydroepiandrosterone, No 3 beta-hydroxysteroid sulfotransferase activity could be detected in cytosol fractions of adrenal glands. Testosterone was sulfated only by hepatic cytosol fractions. All three tissues contained estrogen sulfotransferase activity. These data suggest that the 3 beta-hydroxysteroid sulfotransferase of seminiferous tubules is distinct from the 3 beta-hydroxysteroid sulfotransferase of liver. These differences may relate to different functions of steroid sulfates in liver and testes.