title: Isoproterenol-induced desensitization of adenylate cyclase in human astrocytoma cells. Relation of loss of hormonal responsiveness and decrement in beta-adrenergic receptors.
abstract: Incubation of human astrocytoma cells (1321N1) with low concentrations of isoproterenol results in a specific loss of responsiveness to catecholamines as evidenced by a decreased accumulation of cAMP in intact cells, a reduction in isoproterenol-stimulated adenylate cyclase activity, and a decrease in beta-adrenergic receptor density, as measured by the specific binding of 125I-hydroxybenzylpindolol. The kinetics of desensitization suggest the involvement of two different reactions. The initial reaction involves a rapid loss of adenylate cyclase activity with little loss of beta-adrenergic receptors. Subsequently, a slower reaction results in the loss of measurable beta-adrenergic receptors. The degree of loss of both parameters was similar after 24 h of desensitization. It is concluded that the loss of beta-adrenergic receptors is an event that occurs as a result of the initial uncoupling of the beta-receptor-linked adenylate cyclase.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D001254:Astrocytoma / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007545:Isoproterenol