[Effect of estradiol on 3',5'-AMP-phosphodiesterase activity in rat uterus. Participation of hormone receptors, the role of guanyl nucleotides].

: Estradiol (10(-7)-2 . 10(-5)M) is shown to inhibit the activity of phosphodiesterase of the soluble fraction of the mature rat womb tissue and to have no effect on the activity of adenylate cyclase of this tissue membrane fraction and on the phosphodiesterase of the tissue of the brain, heart and outer segments of the rod-cell. When blocking the estradiol cytosol receptors by clomiphene there is no inhibitory effect of the hormone on the activity of phosphodiesterase of the womb tissue preparations. Specific binding of estradiol by the cytosol receptors increases in the presence of guanylic nucleotides (10(-5)-10(-4)M); ATP does not affect this process. In the presence of guanyl-5-ilimidodiphosphate (Gpp(NH)p), a nonhydrolyzed analog of GTP, clomiphene does not block receptor binding of estradiol. ATP and GTP (10(-6)-10(-5)M), contrary to Gpp (NH)p, inhibit the phosphodiesterase activity. Independent of their effect on the enzymic activity, all the studied nucleotides partially or completely eliminate the inhibitory effect of estradiol on phosphodiesterase.