title: Dexamethasone regulates the beta-adrenergic receptor subtype expressed by 3T3 L1 preadipocytes and adipocytes.
abstract: The subtype of the beta-adrenergic receptor expressed in 3T3-L1 preadipocytes and adipocytes differentiated with dexamethasone and methylisobutylxanthine was determined by comparing the affinity of the receptors for epinephrine, norepinephrine, and beta-1 and beta-2 selective antagonist, 8-fold more avidly than adipocyte receptors. In contrast, adipocyte beta-receptors had a 10-fold higher affinity for epinephrine than for norepinephrine and complexed the beta-2 selective agonist zinterol with a 20-fold higher affinity than preadipocyte receptors. Hofstee plots and computer analyses of the binding data revealed that the populations of beta-1 receptors in preadipocytes and beta-2 receptors in adipocytes were nearly homogeneous. Preliminary characterizations of the beta-receptor phenotype in (nondifferentiating) 3T3-C2 cells treated with dexamethasone and methylisobutylxanthine and 3T3-422A adipocytes differentiated with insulin indicated that the expression of beta-2 receptors was not correlated with differentiation, but rather with exposure of the cells to dexamethasone and methylisobutylxanthine. The regulator of beta-receptor subtype was identified as the glucocorticoid analog, dexamethasone, by employing 3T3-L1 adipocytes which were stimulated to differentiate with methylisobutylxanthine and insulin. Detailed binding studies showed that under these conditions the adipocyte receptors retain beta-1 character. Subsequent treatment with 0.5 microM dexamethasone promoted the loss of beta-1 receptors, the appearance of beta-2 receptors, and a net 2- to 3-fold increase in the number of beta-receptors. Dexamethasone effected a complete switch from beta-1 to beta-2 subtype at concentrations as low as 2.5 nM while other steroids were ineffective below a concentration of 10 microM.
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004983:Ethanolamines / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C011878:iodohydroxybenzylpindolol; C002904:zinterol; D003907:Dexamethasone; D010869:Pindolol; D007545:Isoproterenol