title: Certain beta-blockers can decrease beta-adrenergic receptor number: II. Down-regulation of receptor number by alprenolol and propranolol in cultured lymphoma and muscle cells.
abstract: We have used two different cultured cell lines--S49 lymphoma cells and BC3H-1 muscle cells--to examine the regulation of beta-adrenergic receptors by receptor antagonists. Rather than an increase ("up-regulation") of receptor number that such antagonists often produce, we found that certain beta-blockers elicit a decrease ("down-regulation") of beta-adrenergic receptors. Alprenolol and propranolol, but not sotalol or ICI 118,551, at concentrations of 10-100 nM down-regulated beta-adrenergic receptors 20-70% following 16-20 hours of treatment of S49 or BC3H-1 cells. Several observations suggest that this phenomenon depends upon beta-receptor interaction, including stereoselectivity [(-)-enantiomers more potent than (+)-enantiomers], blockade of the effect by ICI 118,551, absence of down-regulation of alpha-adrenergic receptors in BC3H-1 cells, and lack of a decrease in beta-adrenergic receptor-independent (forskolin-stimulated) cyclic AMP accumulation in S49 cells. The possibility of retained antagonist interfering with receptor measurement was precluded by the fact that the antagonist-induced decrease in receptor number required several hours incubation and occurred without a prominent change in receptor affinity. The ability of the beta-blockers to elicit down-regulation did not correlate with hydrophobicity of the drugs. Antagonist-induced down regulation of beta-adrenergic receptors did not occur in S49 lymphoma cells that lack the alpha-subunit of Gs, the guanine nucleotide-binding regulatory protein, thus implying a requirement for receptor-alpha s interaction in eliciting beta-receptor down-regulation.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000526:Alprenolol / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology; D009132:Muscles / Q000166:cytology / Q000378:metabolism; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D000526:Alprenolol; D011433:Propranolol; D000242:Cyclic AMP