Electrical and mechanical uterine activity and gap junctions in estrogen-treated oophorectomized sheep

The effects of a single dose (0.1 mg) of 17 beta-estradiol on myometrial electrical activity, intrauterine pressure, and myometrial gap junctions were studied in six chronically instrumented oophorectomized ewes. The intrauterine pressure cycles were analyzed for the maximum rate of rise, peak pressure, and active pressure area, together with the frequency of the cycles and the burst frequency, and related to the gap junction area. 17 beta-estradiol temporarily depressed uterine activity. The period of quiescence was followed by a pronounced increase in all variables of electrical and mechanical activity and also by a rise in gap junction area. The greatest increase in the maximum rate of rise of the intrauterine pressure cycles occurred 24 hours after estrogen and was associated with the maximum increase in gap junction area. These results indicate that a single dose of 17 beta-estradiol induces formation of myometrial gap junctions, which may facilitate the spread of electrical activity over the myometrium and improve coordination of uterine contractility.