Racial Differences in Epinephrine and β 2 -Adrenergic Receptors

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Abstract
This study examined the effects of ethnicity and hypertension on β 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 β-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 β-receptor sensitivity, black hypertensive subjects had the highest β-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 β-receptor density ( r =−.26, P <.05) and sensitivity ( r =−.25, P <.05). There were no group differences in binding affinity to the β-antagonist iodopindolol. The findings support the notion of increased β-adrenergic receptors in hypertension in blacks.