Background: Experimental data from normotensive and hypertensive animals indicate that aging is associated with impaired endothelium-dependent relaxations to acetylcholine, and this possibility appears to be confirmed in the human coronary artery. In the present study, we evaluated the effect of age on endothelial responsiveness in the forearm vessels of either normotensive control subjects or essential hypertensive patients.
Methods and results: Within the normotensive or hypertensive group (n = 53 and n = 57, respectively), subjects were selected with similar blood pressure, plasma cholesterol, and glucose values, and hypercholesterolemic subjects, diabetics, and smokers were excluded. We evaluated forearm blood flow (by strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 micrograms/100 mL per minute), an endothelium-dependent vasodilator, and sodium nitroprusside (1, 2, and 4 micrograms/100 mL per minute), an endothelium-independent vasodilator. Acetylcholine caused a dose-dependent vasodilation that was significantly (P < .01) lower in essential hypertensive patients than in normotensive control subjects. However, a significant negative correlation was observed between acetylcholine-induced vasodilation and patient age in both normotensive (r = -.86, P < .001) and hypertensive (r = -.85, P < .001) patients. In contrast, vasodilation to sodium nitroprusside was similar in normotensive control subjects and essential hypertensive patients with a poorer inverse correlation with patient age (normotensive control subjects, r = -.37; hypertensive patients, r = -.36) compared with acetylcholine.
Conclusions: The present data indicate that there is a blunted response to acetylcholine with advancing age in both normotensive control subjects and essential hypertensive patients, suggesting that aging is associated with reduced endothelium-dependent vasodilation in humans.