Previous studies have shown that insulin may stimulate the release of endothelin (ET) from endothelial cells. This mechanism may contribute to the adverse vascular effects determined by chronic hyperinsulinemia. The aim of this study will be to evaluate the effect of local hyperinsulinemia on ET activity in the forearm circulation. To this purpose, we will assess the forearm blood flow response to ET receptor antagonism in control conditions and during intraarterial infusion of insulin. We will also measure changes in plasma ET-1 levels in response to the different pharmacological stimuli.