Effect of Insulin on Acetylcholine-Induced Vasodilation in Normotensive Subjects and Patients With Essential Hypertension

Background The present study was designed to directly test the vasodilation action of insulin and its relation to endothelium-dependent mechanisms. Methods and Results In 18 normotensive subjects and 27 patients with untreated mild to moderate essential hypertension, we studied the effect of intrabrachial insulin on the changes in forearm blood flow (strain-gauge plethysmography) induced by intrabrachial acetylcholine (at doses of 0.15, 0.45, 1.5, 4.5, and 15 μg · min−1 · dL−1), an endothelium-dependent vasodilator, or sodium nitroprusside (at doses of 1, 2, and 4 μg · min−1 · dL−1), an endothelium-independent vasodilator. Local hyperinsulinemia (deep venous plasma insulin, 48±6 and 51±5 μU/mL in control subjects and hypertensive patients, respectively) did not affect basal forearm blood flow and stimulated forearm glucose extraction (control subjects, 3±1% to 11±2%, P<.001; hypertensive patients, 3±1% to 6±1%, P<.001; P<.01 for the between-group difference). In both normotensive and hypertensive subjects...