“…Oxygen-derived free radicals may impair endotheliumdependent vasodilatation through inactivation of NO or by serving as an EDCF (Rubanyi & Vanhoutte, 1986;Katusic & Vanhoutte, 1989). Acute administration of scavengers of superoxide anion, including superoxide dismutase (Hattori et al, 1991;Tesfamariam & Cohen, 1992;Pieper et al, 1996;Bohlen & Lash, 1993) and the combination of superoxide dismutase with catalase (Pieper et al, 1997) improved or normalized the abnormal endothelium-dependent responses in di erent models of diabetes and during high glucose exposure. Similarly, chronic treatment with probucol (Tesfamariam & Cohen, 1992), N-acetylcysteine (Pieper & Siebeneich, 1998b), vitamin E (Keegan et al, 1995;RoÈ sen et al, 1996) and vitamin C (Ting et al, 1996) prevented the development of endothelial dysfunction in clinical and experimental diabetes.…”