DECREASED CARDIAC BETA-ADRENERGIC RECEPTORS IN DEOXYCORTICOSTERONE-SALT AND RENAL HYPERTENSIVE RATS

The development of experimental deoxycorticosterone-salt (DOCA-salt) and renal artery clip hypertension in rats is associated with alterations in the sensitivity of the myocardium to adrenergic stimulation. We studied β-adrenergic receptors and isoproterenol-stimulated adenylate cyclase in myocardial membranes from hypertensive rats to determine whether this altered sensitivity is associated with any change in β-adrenergic receptors. The specific binding of the β-adrenergic antagonist, 125I-ionohydroxybenzylpindolol, was used to measure numbers and affinities of receptors in myocardial membrane preparations. Cardiac membranes from both DOCA-salt and renal hypertensive rats showed significantly fewer β-receptors than did membranes from control, normotensive rats. Receptor affinity remained unchanged. This decrease was from 110 ± 19 to 49 ± 5 fmol/mg protein for DOCA-salt hypertension and from 110 ± 18 to 75 ± 16 fmol/mg protein for renal artery clip hypertension. Isoproterenol-stimulated adenylate cyclase activity also was lower in membranes from hypertensive rats, whereas basal and fluoride-stimulated activities were unchanged.