Production and characterization of antibodies to gonadotropin-releasing hormone receptor

Antibodies to the gonadotropin-releasing hormone (GnRH) receptor of bovine pituitary membranes have been raised in rabbits by immunization with affinity-purified receptor preparations. These antibodies did not compete with 125I-labeled GnRH analog (Buserelin) for binding to the receptors but did precipitate rat and bovine solubilized receptors labeled with 125I-Buserelin. Binding of the antibodies to the receptors was also demonstrated by immunoprecipitation of 125I-labeled purified receptors and photoaffinity-labeled receptors. The antibodies did not have a GnRH-like activity but rather inhibited, in a dose-dependent manner, GnRH-stimulated luteinizing hormone release from cultured rat pituitary cells. In addition, the antibodies did not inhibit luteinizing hormone release stimulated by high K+ concentration. This suggests that the antibodies recognize domains of the receptor other than the binding site of the hormone and thereby inhibit the biological response. These GnRH receptor antibodies provide a useful tool for studying GnRH receptor structure, function, localization, and biosynthesis.