Abstract
Objectives: Vascular responsiveness to infusions of vasoactive substances varies between ethnic groups. Indians of Asian origin are a rapidly growing ethnic group in the United States but have not been extensively studied. We sought to determine whether there was any difference in venous responsiveness to a local infusion of vasoactive substances between Indians of Asian origin and white subjects. Methods: We used the dorsal hand vein compliance technique to construct full dose-response curves to the β2-agonist isoproterenol (2 to 270 ng/min) in hand veins preconstricted with phenylephrine in 11 young white subjects and in 11 young Asian Indian subjects. In addition, six subjects in each group were randomly selected to have full dose-response curves to nitroglycerin (0.006 to 1485 ng/min) generated. Results: The maximal response (E(max)) to isoproterenol was smaller in Asian Indians (33.9% ± 41.1% in Asian Indians versus 107.0% ± 60.1% in white subjects; p < 0.01). There was no difference in the log of the dose that produced half-maximal venodilation [log(ED50)] between the two groups (1.10 ± 0.57 in Asian Indians versus 1.15 ± 0.50 in white subjects). However, nitroglycerin infusion produced similar responses for both the E(max) and the log(ED50) between the two groups. Conclusion: These results indicate that differences may exist in β-adrenergic responsiveness among white subjects and Indians of Asian origin. Therapy for diseases that use β-adrenergic responses, such as hypertension, must take into account these differential vascular responses because they may affect their efficacy in Asian Indians.