Effects of antihypertensive treatment on endothelial function.

Essential hypertension is characterized by endothelial dysfunction due to reduced availability of nitric oxide (NO) secondary to increased generation of oxygen-free radicals. Some antihypertensive drugs may improve or restore endothelial function independently of their blood pressure lowering effect. The newer generation of β-blockers, such as nebivolol and carvedilol, which provide antioxidant activity, can improve endothelial function in patients with hypertension. Dihydropyridine and non-dihydropyridine calcium antagonists reverse impaired endothelium-dependent vasodilatation in different vascular districts, through a mechanism related to an antioxidant effect. However, conflicting results are found in the brachial artery. Angiotensin-converting enzyme (ACE) inhibitors improve endothelial function in subcutaneous, epicardial, brachial, and renal circulation, but they are ineffective in potentiating the impaired response to acetylcholine in the forearm of hypertensive patients. Angiotensin II receptor antagonists can restore endothelium-dependent vasodilatation to acetylcholine in subcutaneous microcirculation but not in that of the forearm muscle. They also improve basal NO release and decrease the vasoconstrictor effect of endogenous endothelin-1. Large-scale clinical trials are required to definitively demonstrate that treatment of endothelial dysfunction can improve the prognosis of patients with essential hypertension.