Impaired endothelium-dependent relaxation of blood vessels is a common feature in diabetes but the exact underlying mechanisms have not yet been clarified. In the present study, endothelium-dependent vasorelaxation of aortic rings were evaluated in vitro in streptozocin-induced diabetic and age-matched control rats. Moreover, NO synthase activity of aortic endothelial cells was assessed in both diabetic and healthy rats using histochemical staining for NADPH diaphorase activity. The results showed a significant decrease of endothelium dependent relaxation in response to ACh in diabetic rings compared with control. A remarkable attenuation of eNOS activity was also observed in sections of diabetic rat aorta using NADPH diaphorase staining. Furthermore, many endothelial cell membranes were disrupted in diabetic cessations. It can be concluded that a decrease in NOS activity together with a disruption of endothelial cell membranes play a major role in endothelial dysfunction observed in diabetes.

Keywords: Key Words: 1) Diabetes mellitus 2) Nitric oxide synthase 3) Rat aorta

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