Oral L-arginine improves endothelial dysfunction in patients with essential hypertension

Background: L-Arginine is a nitric oxide precursor, which augments endothelium-dependent vasodilatation in hypercholesterolemic humans and animals. Endothelium-dependent vasodilation is attenuated in patients with hypertension; however the effects of oral L-arginine on endothelial function of the conduit arteries in patients with essential hypertension have not previously been investigated. Methods: In a prospective randomized double blind trial, 35 patients with essential hypertension received either 6 g L-arginine (18 subjects) or placebo (17 subjects). Patients were examined for flow-mediated endothelium-dependent dilatation of the brachial artery before and 1.5 h after administration of L-arginine or placebo. At the end of the protocol the nitrate-induced, endothelium-independent vasodilatation was evaluated. Results: Two groups of L-arginine and placebo were similar regarding age, sex, blood lipids, smoking, diabetes, coronary artery disease, body mass index, intima-media thickness of the common carotid artery, clinics blood pressure and baseline brachial artery parameters. Administration of L-arginine or placebo did not change significantly heart rate, blood pressure, baseline diameter, blood flow or reactive hyperemia. L-Arginine resulted in a significant improvement of flow-mediated dilatation (1.7 +/- 3.4 vs. 5.9 +/- 5.4%, P = 0.008) while placebo did not significantly change this parameter (3.0 +/- 2.7 vs. 3.1 +/- 2.2%, P = ns). The effect of L-arginine on flow-mediated dilatation was significantly different from the effect of placebo (P = 0.05). L-Arginine did not significantly influence nitrate-induced dilatation (16 +/- 6.9 vs. 17.7 +/- 6.7%, P = ns). Conclusions: Oral administration of L-arginine acutely improves endothelium-dependent, flow-mediated dilatation of the brachial artery in patients with essential hypertension. The long-term effects of L-arginine in these patients require further investigation. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.