RACIAL-DIFFERENCES IN EPINEPHRINE AND BETA(2)-ADRENERGIC RECEPTORS

This study examined the effects of ethnicity and hypertension on beta(2)-adrenergic receptors and on plasma catecholamines in a group of 77 unmedicated mildly hypertensive and normotensive men. Black hypertensive subjects had the most sensitive and white hypertensive subjects the least sensitive beta-receptors (as assessed by isoproterenol-stimulated cyclic AMP in lymphocytes [P=.02]). In contrast, postreceptor adenylate cyclase activation (as assessed by forskolin stimulation) was similar among groups. As with beta-receptor sensitivity, black hypertensive subjects had the highest beta-receptor density and white hypertensive subjects the lowest (P=.03). Blacks demonstrated lower plasma epinephrine values compared with whites (P=.03). Across all subjects, plasma epinephrine was negatively correlated with beta-receptor density (r= -.26, P<.05) and sensitivity (r=-.25, P<.05). There were no group differences in binding affinity to the beta-antagonist iodopindolol. The findings support the notion of increased beta-adrenergic receptors in hypertension in blacks.