Interaction of progestins with Sertoli cell androgen receptors.

In an attempt to distinguish between possible androgen- and progestin-mediated mechanisms in the Sertoli cell, two steroids previously shown to have high affinity for both progesterone and androgen receptors (U13851, 17 alpha-ethynyl-17-hydroxy-7 alpha-methylestr-4-en-3-one and U6817, 17-hydroxy-19-nor-17 alpha-pregn-4-en-3-one) have been compared with respect to a number of parameters with two steroids having high affinity only for progesterone receptors (U49836, 17 beta-methoxyestr-4-en-3-one and U56902, 17-methoxy-17 alpha-pregn-4-3n-20-yn-3-one). U13851 and U6817 were the most potent competitors for cytosol [3H]-R1881 (17-beta-hydroxy-17-methylestra-4,9,11-triene-3-one) binding sites and nuclear accumulation of label. While U49836 and U56902 were considerably less effective as competitors against [3H]-R1881, they were more effective than U13851 and U6817 as competitors against [3H]-progesterone. Only U13851 and R1881 increased Sertoli cell nuclear RNA polymerase II activity. These data substantiate previous suggestions that progestin binding proteins distinct from androgen receptors may exist in Sertoli cells. Moreover, the data also suggest that progestins which stimulate RNA polymerase II activity do so via androgenic mechanisms.