Effect of the angiotensin II type 1 receptor blocker candesartan on endothelial function in patients with essential hypertension.

Patients with essential hypertension are characterized by impaired basal and agonist-evoked nitric oxide release and increased endogenous endothelin (ET)-1-induced vasoconstriction. To assess whether candesartan, an angiotensin II type 1 receptor blocker, can improve endothelial function, we studied the changes in forearm blood flow (FBF) induced in 15 hypertensive patients and in 15 control subjects by the intrabrachial infusion of N(G)-monomethyl-L-arginine (L-NMMA), norepinephrine, the ET A/B receptor antagonist TAK 044, sodium nitroprusside, and acetylcholine. In hypertensive patients, the FBF study was repeated 2 and 12 months after the start of treatment with candesartan cilexetil (8 to 16 mg daily). Compared with controls (maximal FBF decrease, -46+/-11%), hypertensive patients showed a reduced (P<0.001) vasoconstrictor response to L-NMMA (maximal FBF decrease, -28+/-7%); the response to norepinephrine was only slightly impaired, and the response to sodium nitroprusside was similar to that of controls. Finally, TAK-044 caused greater vasodilation in hypertensive patients (maximal FBF increase, 77+/-9%) than in controls (maximal FBF increase, 17+/-10%). In hypertensive patients, candesartan cilexetil significantly enhanced vasoconstriction to L-NMMA after 2 and 12 months (maximal FBF decrease, 37+/-2% [P<0.05] and 42+/-2% [P<0.001], respectively). The responses to norepinephrine, acetylcholine, and sodium nitroprusside were not modified after 2 months. After 12 months, the responses to acetylcholine and sodium nitroprusside were significantly (P<0.05) enhanced at the highest rates. Vasodilation to TAK-044 was abolished after treatment with candesartan cilexetil; this effect is associated with a reduced plasma ET-1 concentration. This study demonstrated that the angiotensin II receptor blocker candesartan improves tonic nitric oxide release and reduces vasoconstriction to endogenous ET-1 in the forearm of hypertensive patients.