Oestradiol-17 beta both inhibits and stimulates myometrial activity in ewes in vivo

Spontaneous intrauterine pressure cycles were abolished for periods of several hours in ovariectomized non-pregnant ewes within 8 h of an injection of 50 micrograms oestradiol-17 beta. Following the quiescent period, a phase of intense uterine activity ensued for several hours before again being replaced by several hours of quiescence. This active/inactive cycle disappeared after 2-4 days if further daily injections of oestradiol were not given. During the quiescent periods the uterus retained its responsiveness to oxytocin and PGF-2 alpha. Increasing the dose of oestradiol failed to prolong the periods of quiescence.