1995 Volume 18 Issue 3 Pages 227-233
We previously demonstrated that intra-arterial infusion of insulin attenuates vasoreactivity to phenylephrine and angiotensin II in the forearm of normotensive humans, which suggests that the pressor effects of insulin via sympathetic activation may be offset in peripheral arteries. In the present study, we investigated the effects of insulin on vasoreactivity in hypertensive humans. Seven male patients with essential hypertension (age, 26±2yr; blood pressure, 159±4/103±4mmHg; mean±SEM) were studied. We measured forearm blood flow by a strain gauge plethysmograph while infusing phenylephrine (1, 4, 12nmol/min) and angiotensin II (5, 10, 20pmol/min) locally into the brachial artery before and during simultaneous intra-arterial infusion of human insulin (0.15mU/kg/min). Forearm vascular resistance was calculated from directly measured arterial pressure and forearm blood flow. Intra-arterial infusion of insulin raised the local plasma insulin level without changing the blood glucose level, basal forearm blood flow, or forearm vascular resistance. Phenylephrine and angiotensin II increased forearm vascular resistance dose-dependently before and during insulin infusion. In contrast to the previous results in normotensive subjects, locally infused insulin did not attenuate vasoconstrictive responses to phenylephrine and angiotensin II in patients with essential hypertension. These results suggest that the balance between the pressor and depressor effects of insulin might be altered in favor of a pressor effect in patients with hypertension. (Hypertens Res 1995; 18: 227-233)
