Effects of estrogen treatment and inhibition of prostanoid synthesis on myometrial activity and gap junction formation in the oophorectomized ewe.

The objective was to elucidate the functional relationship between estradiol-induced changes in myometrial activity, uterine prostanoid synthesis, and gap junction formation in vivo. The study design was as follows. The effects of inhibition of prostanoid synthesis with naproxen on formation of gap junctions and coordination of electrical and mechanical myometrial activity induced by estradiol-17 beta were investigated in 6 chronically instrumented oophorectomized ewes. Prostanoid metabolites were measured in arterial and uterine venous plasma. Myometrial biopsies were obtained to determine gap junction area. The results were that intraarterial administration of 0.1 mg of estradiol-17 beta was followed by a significant increase in maximum rate of rise of the intrauterine pressure cycles and a significant decrease in conduction time of bursts of electrical activity; this response was not altered by pharmacologic inhibition of uterine prostanoid synthesis using naproxen. Estradiol administration during continuous naproxen infusion increased gap junction area. The conclusion is that improved coordination of myometrial activity and formation of myometrial gap junctions induced by estradiol is not mediated by prostaglandins.