Previous studies have shown that the endothelium regulates vascular tone by modulating the activity of vascular smooth muscle. It has also been demonstrated that the endothelium plays an important role in atherosclerosis and animal models of hypertension. The present study was designed to determine whether patients with essential hypertension have an endothelium-dependent abnormality in vascular relaxation. For this purpose, we have utilized intra- arterial infusion of acetylcholine (an endothelium-dependent vasodilator) and sodium nitroprusside (a direct smooth muscle dilator) in hypertensive patients and in a control group of normal volunteers. The results of this study suggest that patients with essential hypertension have an impairment in endothelial-mediated vascular relaxation that may either cause or exacerbate the hypertensive process.
