Impaired forearm vasodilatation by acetylcholine in patients with hypertension

The aim of this study was to examine if vasodilatory responses to acetylcholine or sodium nitroprusside are altered in subjects with essential hypertension. In patients with essential hypertension (mean BP; 121 +/- 4 mmHg, n = 14) and age-matched control subjects (mean BP; 88 +/- 3 mmHg, n = 10), the forearm vasodilatory responses to acetylcholine and sodium nitroprusside were examined. The brachial artery was cannulated with a cannula through which drugs were locally infused. During the drug infusions, forearm blood flow was continuously measured using plethysmography. Basal forearm vascular resistance was higher in patients with essential hypertension than in control subjects (27.5 +/- 3.8 vs 13.8 +/- 1.7 units, P less than 0.01). The increases in forearm blood flow or decreases in forearm vascular resistance in response to the infusions of acetylcholine were smaller in patients with essential hypertension than in control subjects (P less than 0.01). However, the increases in forearm blood flow or decreases in forearm vascular resistance in response to the infusions of sodium nitroprusside were similar for the 2 groups. These results may suggest that the endothelium-dependent vasodilatory response to acetylcholine in the forearm resistance arteries is impaired in patients with essential hypertension.