Myocardial beta-receptors in experimental renal and aortic coarctation hypertensive rabbits

We investigated the effect of inducing two-kidney, one clip (2K, 1C) and aortic coarctation (AC) hypertension in rabbits, on myocardial beta-adrenoreceptor number and affinity, using 3H-dihydroalprenolol as a beta-ligand. Six weeks after surgery, mean arterial blood pressures were: sham-operated controls C, 75.6 +/- 2.3 mmHg (n = 11); 2K-1C 96.3 +/- 2.5 mmHg (n = 6, P less than 0.005); and AC, 114.1 +/- 4.8 mmHg (n = 10, P less than 0.0005). Bmax values at six weeks for C, 2K,-1C and AC were 234.5 +/- 35.7, 139.0 +/- 10.3 (P less than 0.05) and 121.0 +/- 12.8 (P less than 0.005) fmol/mg protein respectively. There were no differences in KD. Both 2K, 1C and AC hypertension significantly decreased myocardial beta-receptor density; this may be a 'down-regulatory' response to increased circulating or myocardial catecholamine concentrations or to enhanced sympathetic activity.