Luteinizing hormone-releasing hormone, ovariectomy, and silastic vaginal rings in the Rhesus monkey

The interaction of estradiol and luteinizing hormone-releasing hormone (LRH) may be a critical physiologic mechanism regulating the occurrence of ovulation in many species. These studies were conducted to assess (1) the effects of intramuscular injections of LRH in the intact female rhesus monkey and (2) the effects of estradiol in a Silastic delivery system in ovariectomized female rhesus monkeys. No changes in blood levels of luteinizing hormone (LH) were detected in response to 200 micrograms of LRH. Ovulation did not occur 48 hours after treatment. Ovariectomy decreased estradiol, increased LH, and had no effect on prolactin concentrations in sera. Insertion of a vaginal ring containing 10% estradiol increased blood estradiol levels 100-fold. Serum prolactin levels were unaffected; however, LH concentrations were altered in a multiphasic fashion. After the ring had been in place for 15 days, vaginal blood similar to menstrual flow was observed following removal.