The influence of L-arginine on vascular endothelial function at rest and during sympathetic activation

Endothelial dysfunction, arterial stiffness and hypertension increase the risk of cardiovascular disease. Stiff arteries are a consequence of chronic systolic hypertension and atherosclerosis. The resulting increase in peripheral resistance due to a narrow arterial lumen increases the rate pressure product and demand on the heart. One way to reduce the demand on the heart is to lower peripheral resistance by vasodilating the peripheral vessels. L-arginine is an endothelial substrate used to produce nitric oxide, a potent vasodilator. Vasodilation increases arterial lumen diameter through smooth muscle cell relaxation, improving arterial elasticity, blood flow and lowering blood pressure. Slower pulse wave transit times in the arterial tree indicate arterial elasticity decreasing demand on the heart and decreasing risk for cardiovascular disease. While L-arginine may stimulate nitric oxide production and reduce peripheral resistance, no known studies have investigated L-arginine supplementation on arterial stiffness in healthy individuals. In order to establish the effects oral L-arginine supplementation on pulse wave transit times, this study hypothesizes (1) L-arginine will decrease peripheral arterial stiffness in young healthy subjects, (2) L-arginine will decrease peripheral arterial stiffness in active tissue, and (3) L-arginine will decrease peripheral arterial stiffness in inactive tissue. The hypotheses tested acute L-arginine supplementation during three different conditions: rest, reactive hyperemia and ischemic handgrip exercise. Fifteen subjects were recruited (N=15), and visited the laboratory on two separate days: the first day without L-arginine supplementation and the second day, a dosage of 70 mg per kg lean body mass was given as a water L-arginine solution. No differences were found comparing the three conditions with L-arginine supplementation. This study concludes L-arginine does not decrease peripheral arterial stiffness in young healthy subjects and does not decrease peripheral arterial stiffness with active and inactive tissue.