Modulation by hydrogen peroxide of noradrenaline-induced contraction in aorta from streptozotocin-induced diabetic rat.

Hydrogen peroxide (H(2)O(2)) is known to modify vascular tone in various preparations and its production is elevated in the diabetic aorta. We have investigated its possible involvement in regulation of the noradrenaline-induced contractile response in aorta from streptozotocin-induced diabetic rats. In diabetic but not in control aorta, the noradrenaline-induced contraction was significantly enhanced by catalase and significantly inhibited by polyethylene-glycolated superoxide dismutase. Adding catalase to the superoxide dismutase prevented the latter's attenuation of the contraction. In the presence of N(G)-nitro-L-arginine, the noradrenaline-induced contraction of aorta from diabetic rats, but not from controls, was inhibited by catalase treatment. Noradrenaline increased the nitrite and nitrate levels in the perfusates from control and diabetic aortic strips. In the latter, the noradrenaline-induced nitrite and nitrate level was significantly enhanced by incubation with superoxide dismutase but not by incubation with catalase plus superoxide dismutase. Thus, endogenously produced H(2)O(2) may be an important factor in the regulation of aortic tone in diabetic rats. Enhanced production of H(2)O(2) in the aorta from diabetic rats may seem contribute to the endothelial generation of nitric oxide and vasoconstrictor prostanoids.