Variability in vascular responsiveness between Mexican-Americans and White Americans

Ethnic differences in vascular adrenergic responsiveness have been implicated to be a potentially important mechanism which may be responsible for some of the variations in haemodynamic patterns between races. These differences may account for the variability in the prevalence of hypertension in different groups. The main aim of this study was to determine whether there was a difference in venous responsiveness to the vasoactive agents, phenylephrine and isoproterenol, between Mexican-Americans and White Americans. Isoproterenol is a potent non-selective beta-adrenergic agonist, phenylephrine is an alpha1-selective adrenergic agonist. Using the dorsal hand vein compliance technique, dose-response curves were constructed for the two vasoactive agents in 10 Mexican-American and 10 White American volunteers. The maximal venoconstriction for phenylephrine in the Mexican-American group was significantly less than that of the Whites in the study (71.2 +/- 20.1% vs 89.4 +/- 10.9%, P < 0.05). The log ED50 for isoproterenol in the Mexican-American group was also significantly greater than that for Whites (1.68 +/- 0.35[47.6 ng/min] vs 1.19 +/- 0.55[15.5 ng/min], P < 0.05). These results suggest that Mexican-Americans have a differential responsiveness to adrenergic vasoactive agents compared to White Americans and may be protected from the development of hypertension.