Binding of Dihydroatprenolol and Dihydroergocryptine to Sheep Myometrium

Abstract

For a better understanding of the action of catecholamines on the uterus, the quanity and affinity of binding of tritiated dihydroergocryptine (DHE) and dihydroalprenolol (DHA) to sheep myometrial membranes were studied in vitro for ewes on various days of the estrous cycle and in estrogen- and progesterone[P4]-treated ovariectomized ewes. The DHE appeared to bind specifically to an .alpha.-adrenoceptor, and more DHE was bound during the luteal phase of the estrous cycle than at estrus. Treatment of ovariectomized ewes with P4 increased binding of DHE. The DHA appeared to bind specifically to .beta.-adrenoceptor, and more DHA was bound on day 3 than during the luteal phase of the estrous cycle. Treatment of ovariectomized ewes with estradiol increased binding of DHA. The affinity of DHE (Kd = 3 nM) and of DHA (Kd = 5 nM) for sheep myometrial membranes was high and did not vary significantly throughout the estrous cycle. Estradiol and P4 may modify uterine contractility during the estrous cycle by their action on .alpha.- and .beta.-adrenoceptors.