The status of beta-adrenergic receptors was investigated in A431 cells exposed to chronic stimulation by the beta-adrenergic agonist, (-)-isoproterenol. Specific binding of beta-adrenergic antagonist (-)-[125I]iodocyanopindolol declined to 60-80% below control values within 12 h of agonist treatment. This decline in ligand binding was also observed in high-speed membrane fractions prepared from agonist-treated cells. Immunoblots probed with anti-receptor antibodies revealed both that beta-adrenergic receptors from untreated and treated cells migrated as 65,000-Mr peptides and that the cellular complement of receptor was unchanged. Indirect immunofluorescence localization of beta-adrenergic receptors was comparable in control (untreated) cells and cells challenged with (-)-isoproterenol for 1, 12, or 24 h. Thus receptor complement, migration on SDS/polyacrylamide-gel electrophoresis, and localization in situ are largely unaffected by agonist stimulation. Receptor binding of antagonist radioligands, in contrast, is markedly down-regulated in cells stimulated chronically with beta-adrenergic agonists. These data argue in favour of agonist-induced alteration(s) in the conformation of the receptor that preclude radioligand binding rather than agonist-induced receptor sequestration and/or degradation.
Research Article|October 15 1989
Localization of β-adrenergic receptors in A431 cells in situ. Effect of chronic exposure to agonist
H Y Wang;
Biochem J (1989) 263 (2): 533-538.
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H Y Wang, M Berrios, C C Malbon; Localization of β-adrenergic receptors in A431 cells in situ. Effect of chronic exposure to agonist. Biochem J 15 October 1989; 263 (2): 533–538. doi: https://doi.org/10.1042/bj2630533
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