The effects of sustained-release-L-arginine formulation on blood pressure and vascular compliance in 29 healthy individuals.

Vascular endothelial function is crucial to cardiovascular function and thus to blood perfusion to the heart and throughout the body. A number of substances are produced and secreted by vascular endothelial cells, the most important of which is nitric oxide, a potent regulator of vascular function. Nitric oxide diffuses from endothelial cells into underlying smooth muscle, causing relaxation, which results in vasodilation. When this process is inhibited or inadequate the arteries cannot dilate as necessary, resulting in hypertonicity and reduced blood flow. Such endothelial dysfunction also causes increased platelet and monocyte adhesiveness and smooth muscle proliferation, processes thought to be at the genesis of atherosclerotic plaque formation. Since L-arginine is the body's only substrate for nitric oxide synthesis, adequate L-arginine must be present for proper nitric oxide production. In this open label trial, a group of 29 asymptomatic individuals were given L-arginine (1,050 mg, as Perfusia-SR, a sustained-release preparation) twice daily (total 2.1 g daily) for one week. Systolic blood pressure was reduced in 62 percent of participants compared to baseline, with a non-significant mean decrease in all patients of 4 mm Hg. Diastolic blood pressure was reduced in 69 percent of participants, with a mean reduction of 3.7 mm Hg (p = 0.005). In the 10 individuals who were borderline or hypertensive (systolic > 130 or diastolic > 85), there was a mean systolic reduction of 11 mm Hg (p = 0.05), while normotensives (n = 19) had a mean systolic decrease of only 0.22 mm Hg. Diastolic blood pressure was decreased a non-significant 4.9 mm Hg in borderline or hypertensives and 4.5 mm Hg in normotensives (p = 0.026). Vascular elasticity relates to endothelial function, and can be measured non-invasively. At baseline and follow-up, vascular compliance was assessed via digital pulse wave analysis (DPA; Meridian Medical). After one week, pulse wave analysis showed a significant increase in large artery compliance (mean 23% improvement; p = 0.02) and a non-significant increase in small artery compliance (mean 23% improvement; p = 0.15). This study demonstrates blood pressure reductions, especially in patients with borderline or frank hypertension, as well as improved vascular compliance - an indicator of improved endothelial function and perfusion - after a one-week trial of sustained-release L-arginine. Poor endothelial function due to inadequate endothelial nitric oxide production is present in hypertension, as well as in numerous other aspects of cardiovascular disease, including angina, erectile dysfunction, cerebrovascular disease, and peripheral vascular disease. This is the first study showing a moderate dose of sustained-release L-arginine can improve endothelial function and blood pressure.