IMPAIRED BETA(2)-ADRENERGIC AGONIST-INDUCED VENODILATION IN INDIANS OF ASIAN ORIGIN

Objectives: Vascular responsiveness to infusions of vasoactive substan ces varies between ethnic groups, Indians of Asian origin are a rapidl y growing ethnic group in the United States but have not been extensiv ely studied, We sought to determine whether there was any difference i n venous responsiveness to a local infusion of vasoactive substances b etcveen Indians of Asian origin and white subjects. Methods: We used t he dorsal hand vein compliance technique to construct full dose-respon se curves to the beta(2)-agonist isoproterenol (2 to 270 ng/min) in ha nd veins preconstricted with phenylephrine in 11 young white subjects and in 11 young Asian Indian subjects. In addition, six subjects in ea ch group were randomly selected to have full dose-response curves to n itroglycerin (0.006 to 1485 ng/min) generated. Results: The maximal re sponse (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(ED(50))] between the two groups (1.10 +/- 0.57 in Asian Indians versus 1.15 +/- 0.50 in white subjects). How ever, nitroglycerin infusion produced similar responses for both the E (max) and the log(ED(50)) between the two groups. Conclusion: These re sults indicate that differences may exist in beta-adrenergic responsiv eness among white subjects and Indians of Asian origin. Therapy for di seases that use beta-adrenergic responses, such as hypertension, must take into account these differential vascular responses because they m ay affect their efficacy in Asian Indians.