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(Circulation. 2004;109:3191-3195.)
© 2004 American Heart Association, Inc.

Clinical Investigation and Reports

Ethnic Differences in the Vasoconstrictor Activity of Endogenous Endothelin-1 in Hypertensive Patients

From the National Heart, Lung, and Blood Institute, Bethesda, Md (U.C., C.C., J.A.P.); Università Cattolica del Sacro Cuore, Rome, Italy (C.C.); and Washington Hospital Center, Washington, DC (U.C., J.A.P.).

Correspondence to Dr Julio A. Panza, Washington Hospital Center, 110 Irving St, NW, Suite 2A 74, Washington, DC 20010. E-mail julio.a.panza{at}medstar.net

Received January 21, 2004; accepted March 13, 2004.

Background— The pathogenesis of essential hypertension in blacks may differ from that in whites. In particular, black patients usually present with a salt-sensitive, low-renin form, which in animal models is associated with enhanced activity of endothelin-1 (ET-1). This study aimed to assess whether ethnic differences exist in the vascular activity of ET-1 in normotensive and hypertensive blacks and whites.

Methods and Results— Forearm blood flow (FBF) responses to intraarterial infusion of an ET_A receptor blocker (BQ-123) were analyzed by plethysmography in 37 normotensive patients and 27 hypertensive patients according to race. BQ-123 did not affect FBF in normotensive subjects (P=0.30), whereas it produced significant vasodilation in hypertensive subjects (P<0.001). In normotensives, FBF response to BQ-123 was similar in white (n =22) and black (n =15) patients (P=0.85). In contrast, in hypertensive patients, the vasodilator effect of ET_A receptor blockade was significantly higher in blacks (n =13) than in whites (n =14) (P=0.01). To rule out differences in smooth muscle reactivity, the effects of race on FBF responses to exogenous ET-1 were analyzed in the hypertensive subgroups. Endothelin-1 induced a significant vasoconstriction in both white (n =7) and black patients (n =5) (both P<0.001), without differences between them (P=0.46). In 8 black hypertensives, the response to selective ET_A blockade was not modified by nonselective blockade of ET-1 receptors by co-infusion of BQ-123 and BQ-788 (P=0.66).

Conclusions— Hypertensive blacks have enhanced ET_A-dependent vasoconstrictor tone, probably related to increased production of ET-1. Given the negative vascular effects of ET-1, this abnormality may contribute to the pathogenesis of hypertension and its complications in black patients.

Key Words: hypertension • endothelin • endothelium

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