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 hypertensi ve subjects had the most sensitive and white hypertensive subjects the least sensitive beta-receptors (as assessed by isoproterenol-stimulat ed cyclic AMP in lymphocytes [P=.02]). In contrast, postreceptor adeny late cyclase activation (as assessed by forskolin stimulation) was sim ilar among groups. As with beta-receptor sensitivity, black hypertensi ve subjects had the highest beta-receptor density and white hypertensi ve subjects the lowest (P=.03). Blacks demonstrated lower plasma epine phrine values compared with whites (P=.03). Across all subjects, plasm a epinephrine was negatively correlated with beta-receptor density (r= -.26, P<.05) and sensitivity (r=-.25, P<.05). There were no group dif ferences in binding affinity to the beta-antagonist iodopindolol. The findings support the notion of increased beta-adrenergic receptors in hypertension in blacks.