Decreased cardiac beta-adrenergic receptors in deoxycorticosterone-salt and renal hypertensive rats.

Abstract

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 beta-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 beta-adrenergic receptors. The specific binding of the beta-adrenergic antagonist, 125I-iodohydroxybenzylpindolol, 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 beta-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.