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.