Vasoconstriction to endogenous endothelin-1 is increased in the peripheral circulation of patients with essential hypertension

Background-In humans, endothelin (ET)-1 could be implicated in the pathophysiology of several cardiovascular diseases, including essential hypertension. We therefore evaluated the role of ET-1 in control of vascular tone in essential hypertension. Methods and Results-We used strain-gauge venous plethysmography to test changes in forearm blood Row induced by intrabrachial infusion of TAK-044 (10, 30, and 100 mu g.100 mL(-1).min(-1)), an ETA/ETB receptor antagonist, or sodium nitroprusside (1 and 2 mu g.100 mL(-1).min(-1)), a vasodilator that acts on smooth muscle cells, in hypertensive patients and healthy controls (n=10 in each group). The NO pathway was also evaluated by infusion of N-G-monomethyl-L-arginine, (L-NMMA; 10, 30, and 100 mu g.100 mL(-1) min(-1)), an NO synthase inhibitor, and nonpinephrine (3, 9, and 30 ng.100 mL(-1).min(-1)) as control. Immunoreactive plasma ET-I was measured by radioimmunoassay. In hypertensive patients, TAK-044 caused a vasodilation that was significantly (P<0.01) increased compared with normotensive subjects. Moreover, vasoconstriction to L-NMMA was significantly (P<0.01) decreased in hypertensive patients compared with controls. In contrast, the vascular responses to sodium nitroprusside and norepinephrine, as well as levels of immunoreactive plasma ET-1, were similar in hypertensive patients and controls. In the study population, vasodilation to TAK-044 and vasoconstriction to L-NMMA showed an inverse correlation (r = -0.56, P<0.05). Conclusions-These results indicate that TAK-044 caused a greater degree of vasodilation in the forearm vessels of essential hypertensive patients compared with normotensive subjects, an alteration associated with decreased tonic NO release.