Effect of increased availability of endothelium-derived nitric oxide precursor on endothelium-dependent vascular relaxation in normal subjects and in patients with essential hypertension.

BACKGROUNDPatients with essential hypertension have a deficit in the endothelium-derived nitric oxide system that results in impaired endothelium-dependent vascular relaxation. The objective of this study was to determine whether this abnormality is caused by a deficiency of substrate for nitric oxide synthesis.METHODS AND RESULTSThe vascular responses to acetylcholine (an endothelium-dependent vasodilator infused at 7.5, 15, and 30 micrograms/min) and sodium nitroprusside (a direct smooth muscle dilator infused at 0.8, 1.6, and 3.2 micrograms/min) were studied during combined administration of dextrose 5% or L-arginine (substrate for nitric oxide synthesis infused at 40 mumol/min) in 12 normal control subjects (seven men and five women; age, 49.3 +/- 7 years) and 14 hypertensive patients (nine men and five women; age, 48.4 +/- 7 years). In addition, the effect of D-arginine (stereoisomer of arginine that is not a precursor of nitric oxide) on the vascular responses to acetylcholine was studied in eight n...