GnRH Receptors: Identification, Localization and Implications for Biological Function

Abstract

Gonadotropin-releasing hormone (GnRH) is a hypothalamic decapeptide, which stimulates gonadotropin release from the anterior pituitary. The first step in GnRH action (Conn et al., 1981b) is its recognition by specific binding sites (receptors) at the surface of gonadotrope cells. The interaction of GnRH with pituitary membrane preparations or cultured pituitary cells has been studied in detail by using radioiodinated, metabolically stable GnRH analogs (Clayton et al., 1978; Conne et al., 1979; Clayton and Catt, 1980, 1981; Marian and Conn, 1980; Naor et al., 1980; Hazum, 1981a; Marian et al., 1981; Meidan and Koch, 1981a). These studies have indicated the presence of a single class of high-affinity binding sites for both agonists and antagonists of GnRH in the pituitary. Recently, the presence of similar high affinity binding sites have been shown in the ovary and testis (reviewed by Clayton and Catt, 1981; Hsueh and Jones, 1981; Hazum, 1983). Characterization of the GnRH-receptor in the pituitary have indicated that the receptor is a glycoprotein which contains sialic acid residues (Hazum, 1982a) and that membrane phospholipids are involved in the interaction between the hormone and the receptor (Hazum et al., 1982a).