Insulin attenuates vasoconstriction by noradrenaline, serotonin and potassium chloride in rat mesenteric arterioles.

We investigated the effect of insulin on the vascular reactivity to noradrenaline, serotonin and potassium chloride in rat mesenteric resistance arterioles in vitro. Mesenteric artery segments were placed in a myograph system. Sensitivity to noradrenaline, serotonin and KCl was tested after an equilibration at 37 degrees C. Thereafter, arteries were incubated with buffer alone or with insulin (40, 100, 250 and 400 mU/ml) for one hour at 37 degrees C. Sensitivity to the three vasoconstrictors was retested. Incubation with noradrenaline, serotonin and KCl resulted in a dose dependent increase in wall force. Exposure with buffer did not change the shape of the dose-response-curve. The same was true for the lowest dose of insulin (40 mU/ml). However, incubation with insulin at concentrations of 100, 250 and 400 mU/ml led to a reduction in wall force by 37-77%. The reduction in the slope of the curve and the maximal response suggest a non-competitive inhibition. Supraphysiological doses of insulin attenuate the vasoconstriction by noradrenaline, serotonin and KCl in rat mesenteric arteries in vitro.