title: Properties of beta-adrenergic receptors of cultured mammalian cells. Interaction of receptors with a guanine nucleotide-binding protein in membranes prepared from L6 myoblasts and from wild-type and cyc- S49 lymphoma cells.
abstract: The radiolabeled agonist [3H]hydroxybenzylisoproterenol ([3H]HBI) and antagonist [125I]iodopindolol ([125I]IPIN) were used to investigate the properties of beta-adrenergic receptors on membranes prepared from L6 myoblasts and S49 lymphoma cells. The high affinity binding of (-)-[3H]HBI to membranes prepared from L6 myoblasts was stereoselectively inhibited by the active isomers of isoproterenol and propranolol. The density of receptors determined with (-)-[3H]HBI was less than that determined with [125I]IPIN. The binding of (-)-[3H]HBI was inhibited by guanine nucleotides, suggesting an agonist-mediated association of the receptor with a guanine nucleotide-binding protein, presumably the stimulatory guanine nucleotide-binding protein (Ns) of adenylate cyclase. Results obtained in studies with membranes prepared from wild-type S49 lymphoma cells and the adenylate cyclase-deficient variant (cyc-) were similar to those obtained in experiments carried out with membranes prepared from L6 myoblasts. Thus, the high affinity binding of (-)-[3H]HBI to membranes prepared from wild-type and cyc- S49 lymphoma cells was stereoselectively inhibited by the active isomers of isoproterenol and propranolol, and was inhibited by GTP. Moreover, the density of sites determined with (-)-[3H]HBI was less than that determined with [125I]IPIN. These results suggest either that cyc- cells contain a partially functional Ns, or alternatively, that the inhibitory guanine nucleotide-binding protein (Ni) is capable of interacting with beta-adrenergic receptors.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008223:Lymphoma / Q000378:metabolism*; D051379:Mice; D009132:Muscles / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D007545:Isoproterenol