Dissociation of effects of hypertrophy from hypertension on cardiac beta-receptors in renovascular hypertensive rats.

Reduction in density of beta-adrenoceptors has been demonstrated in the hypertrophied left ventricle (LV) of renovascular hypertensive rats (RHR). In order to investigate the relative role of cardiac hypertrophy as distinct from hypertension, LV beta-receptors were determined in RHR four days after nephrectomy of the clipped kidney (RHR-Nx) when blood pressure was reduced but hypertrophy still evident; the results were compared with those obtained in age-matched untreated RHR and sham operated rats (SHAM). As expected, blood pressure (BP) was reduced four days after nephrectomy (150 +/- 3 versus 212 +/- 11 mmHg untreated RHR, P less than 0.001) but LV hypertrophy had not regressed (3.07 +/- 0.16 versus 3.58 +/- 0.24 mg/g, NS). Ventricular beta-receptor density was reduced in both RHR (1.601 +/- 0.078 pmol/g) and RHR-Nx (1.667 +/- 0.124 pmol/g) compared with SHAM (2.033 +/- 0.06 pmol/g, P less than 0.05 for both). The dissociation constant (Kd) was not different among the three groups. Thus, the reduction of beta-adrenergic receptors in the hypertrophied LV of RHR persisted even when BP was lowered by nephrectomy, suggesting that hypertrophy per se rather than hypertension accounted for that reduction in cardiac beta-receptors.