INSULIN-MEDIATED VASODILATION - IMPAIRMENT WITH INCREASED BLOOD-PRESSURE AND BODY-MASS

Insulin resistance is associated with hypertension although it is not known if this relationship is casual. Studies have shown that insulin increases skeletal-muscle blood flow despite also increasing sympathet ic activity. To determine whether insulin may act as a direct vasodila tor and whether insulin-mediated vascular effects are altered in hyper tension, we studied insulin-mediated alterations in dorsal-hand-vein c ompliance in normotensive and mild and borderline hypertensive subject s. In phenylephrine pre-constricted vessels, insulin caused a dose-dep endent increase in venous distensibility. Insulin-mediated venodilatio n was significantly impaired in hypertensive subjects. The vasodilator potency of insulin was significantly correlated with both blood press ure and body mass index. Insulin may be an endogenous vasodilator. Fur ther, in hypertensive and obese subjects, impairment of insulin-mediat ed vasodilation may contribute to the increase in peripheral resistanc e characteristic of hypertension.