Beta-adrenergic receptors in chronic alcoholic rat hearts.
Properties of cardiac beta-adrenergic receptors from chronic alcoholic and control rats were studied to determine whether alterations in the receptor contribute to the decreased responsiveness of isolated working alcoholic rat hearts to beta-adrenergic stimulation. The receptors, assessed in crude membrane fractions by the binding of (-)[3H]dihydroalprenolol, did not differ significantly in either number or affinity in alcoholic rats (22.5 +/- 1.9 fmol . mg protein-1; Kd = 0.49 +/- 0.03 nmol . litre-1; n = 7) compared with control rats (25.9 +/- 1.3 fmol . mg protein-1; Kd = 0.55 +/-0.04 nmol . litre-1; n = 7). Competition experiments indicated that there was no difference in the binding affinity of (-)isoprenaline for the alcoholic and control rat heart receptors, nor in the affinity of (-)propranolol for he alcoholic and control rat heart receptors. In the presence of 5' -guanylylimidodiphosphate, the affinity of (-)isoprenaline for the receptors was decreased the same amount in the alcoholic and control rat hearts. These results suggest that the beta-adrenergic subsensitivity of chronic alcoholic rat hearts is mediated by a biochemical mechanism other than a direct alteration of the beta-adrenergic receptor or coupling between the receptor and adenylate cyclase.
D000437:Alcoholism / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D006801:Humans; D007545:Isoproterenol / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011433:Propranolol / Q000378:metabolism; D051381:Rats; D011941:Receptors, Adrenergic / Q000032:analysis*; D011943:Receptors, Adrenergic, beta / Q000032:analysis*
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D007545:Isoproterenol