“…Indeed, a considerable body of evidence now suggests that in type I diabetes, the observed impairment of endothelial function may involve inactivation of NO by oxygen-derived free radicals (Meraji et al, 1987;Hattori et al, 1991;Pieper et al, 1992;Tesfamariam, 1994;Keaney and Vita, 1995;Kamata et al, 1996a;Ooboshi et al, 1997;Kobayashi and Kamata, 1999a, 2002b. In experimental models of type I diabetes, an enhancement of NO production (which in such models is diminished by superoxide anion) and dismutation of free radicals has generally been found to improve impaired endothelium-dependent relaxation (Rubanyi and Vanhoutte, 1986;Marshall et al, 1988;Kobayashi and Kamata, 2001). Convincing evidence indicates that the major enzymatic sources of vascular superoxide are NAD(P)H oxidase, xanthine oxidase, and uncoupled NOS (Landmesser and Harrison, 2001).…”