Biology of Reproduction, Vol 24, 831-838, Copyright © 1981 by Society for the Study of Reproduction

Binding of Dihydroalprenolol and Dihydroergocryptine to Sheep Myometrium

¹ U. S. Department of Agriculture, Beltsville, Maryland 20705

For a better understanding of the action of catecholamines on the uterus, the quantity 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 (Experiment 1) and in estrogen- and progesterone-treated ovariectomized ewes (Experiment 2). 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 progesterone increased binding of DHE. The DHA appeared to bind specifically to a 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 (K_D = 3 nM) and of DHA (K_D = 5 nM) for sheep myometrial membranes was high and did not vary significantly throughout the estrous cycle. Estradiol and progesterone may modify uterine contractility during the estrous cycle by their action on alpha and beta adrenoceptors.

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