Endothelial dysfunction in hypertension.
Endothelial cells release both relaxing and contracting factors that modulate vascular smooth muscle tone and also participate in the pathophysiology of essential hypertension. Endothelium-dependent vasodilation is regulated primarily by nitric oxide but also by an unidentified endothelium-derived hyperpolarizing factor and by prostacyclin. Endothelium-derived contracting factors include endothelin-1, vasoconscrictor prostanoids, angiotensin II and superoxide anions. Under physiological conditions, there is a balanced release of relaxing and contracting factors. The balance can be altered in cardiovascular diseases such as hypertension, atherosclerosis, diabetes and other conditions, thereby contributing to further progression of vascular and end-organ damage. In particular, endothelial dysfunction leading to decreased bioavailability of nitric oxide impairs endothelium-dependent vasodilation in patients with essential hypertension and may also be a determinant for the premature development of atherosclerosis. Different mechanisms of reduced nitric oxide activity have been shown both in hypertensive states and several cardiovascular diseases, and endothelial dysfunction is likely to occur prior to vascular dysfunction. Thus, the strategies currently used to improve endothelial dysfunction may result in decreased morbidity and mortality in hypertensive patients.