Acetylcholine in Essential Hypertension

Patients with essential hypertension show impaired endothelium-dependent vasodilation induced by acetylcholine. Because dietary potassium supplementation increases endothelium-dependent relaxations to acetylcholine in hypertensive rats, we designed the present study to investigate whether potassium increases endothelium-dependent vasodilation in essential hypertensive patients. Therefore, in patients with essential hypertension (n = 13) and in normotensive control subjects (n = 13) we evaluated the effect of intrabrachial potassium chloride (0.2 mmol/min) on forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 jtg/100 mL forearm tissue per minute). In both groups of patients, potassium chloride infusion augmented local plasma potassium concentrations. Furthermore, in essential hypertensive patients but not in normotensive subjects it increased the vasodilating effect of the first three infusion rates of acetylcholine. In contrast, in seven adjunctive essential hypertensive patients, potassium chloride did not alter intrabrachial sodium nitroprusside-inI t has been well documented that endothelial cells play a key role in modulating vascular tone, mainly through the production of an endothelium-derived relaxing factor, identified with nitric oxide, that is synthesized by endothelial cells from the degradation of L-arginine into citrulline. In animal models of hypertension, endothelium-dependent relaxation is impaired," and even human hypertension is probably characterized by a defect in endothelial function, as suggested by several observations* demonstrating a reduced vascular response to the endothelium-dependent vasodilator acetylcholine. Because in different types of experimental hypertension dietary potassium supplementation can improve endothelial responsiveness to acetylcholine, we designed the present study to investigate whether potassium might improve endothelium-dependent vasodilation in human hypertension and normotensive control subjects.