Inadequate corpus luteum function after the induction of ovulation in anoestrous ewes by LH-RH or an LH-RH agonist

Abstract

Scottish Blackface ewes were given LHRH (3 .times. 30 .mu.g i.v., at 90 min intervals) or D-Ser-(But)6-des-Gly10 LHRH ethylamide (LHRH antagonist) as a single injection (8 or 40 .mu.g) during anestrus. Ovulation as judged by laparoscopy occurred in 8 of the 27 animals. Despite the fact that the LHRH agonist induced a greater release of LH [lutropin] and FSH the different treatments had no effect on the number of ewes ovulating and within each treatment group there was no apparent difference in the amounts of gonadotropins released between the ewes that did or did not ovulate. All ovulations resulted in the formation of CL [corpora lutei] associated with plasma progesterone concentrations of < 1 ng/ml (1-5 ng/ml in the normal luteal phase). In comparison with CL of the normal cycle the induced CL were of lower weight and had reduced progesterone content and ability to secrete progesterone in vitro. The binding of human chorionic gonadotropin was equivalent to that of normal CL. The inadequate CL formed in anestrous ewes after a single LHRH injection apparently have not developed the ability to synthesize and secrete progesterone despite the presence of normal amounts of LH receptors.