Luteal Desensitization: Hormonal Regulation of LH Receptors, Adenylate Cyclase and Steroidogenic Responses in the Luteal Cell

Abstract

Regulation of peptide hormone receptors and target cell responses by increased concentrations of the homologous hormone has been demonstrated in a number of endocrine-dependent tissues (1–6). This process, described variously as desensitization, tachyphylaxis, refractoriness, tolerance, and down-regulation, is particularly marked in the testis and ovary following exposure to elevated gonadotropin levels (5–12). The finding that insulin (1) and growth hormone (2) are able to regulate their own receptor sites in target cells was followed by the demonstration of an inverse relationship between ligand concentration and receptor number for several other hormones, including catecholamines (3), thyrotropin releasing hormone (4) and gonadotropins (5–12). Although such negative regulation of receptor sites is now recognized to be a wide-spread property of peptide hormones, it should be noted that certain hormones, such as prolactin (13) and angiotensin (14) exert positive regulation upon their receptor sites, with an increase in binding capacity of the target cells in response to elevated hormone concentration.