title: Photo-induced inactivation and uncoupling of gonadotropin receptors in rat ovarian plasma membrane.
abstract: Suspensions of purified rat ovarian plasma membranes were irradiated by high-intensity light in the cold. This treatment gradually reduced the ability of the membrane receptor to bind 125I-labeled human chorionic gonadotropin and the ability of adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) to respond to luteinizing hormone, follicle-stimulating hormone, human chorionic gonadotropin and prostaglandin E2. In contrast adenylate cyclase activity stimulated by NaF or guanosine 5'(beta, gamma-imido)triphosphate (p(NH)ppG) was significantly more resistant to irradiation. Human chorionic gonadotropin protected the binding site from light-induced damage, but not the ability of the hormone to activate adenylate cyclase. Irradiation destroyed close to 50% of unoccupied guanosine nucleotide binding sites but apparently did not induce massive covalent binding of nucleotides to membrane components. It is suggested that high-intensity light induces damage to two separate sites in the adenylate cyclase system. One affects hormone binding and is presumably associated with the hormone receptor, the second interferes with coupling but at a step proximal to regulation of adenylate cyclase by GTP binding protein.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D007700:Kinetics; D008027:Light; D007986:Luteinizing Hormone / Q000494:pharmacology; D010053:Ovary / Q000378:metabolism* / Q000528:radiation effects; D011458:Prostaglandins E / Q000494:pharmacology; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D006063:Chorionic Gonadotropin; D011458:Prostaglandins E; D011956:Receptors, Cell Surface; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000262:Adenylyl Cyclases