Toxic Responses of the Plasma Xanthine Oxidase (XO)
Xanthine oxidase is an important source of free oxygen radicals, especially superoxide anions, because it is able to use molecular oxygen instead of NAD+ as electron acceptor in the two-step conversion of hypoxanthine to uric acid. This reaction mechanism has been confirmed in both animal and human studies (Connors et al. 1981; Brown et al. 1988; Ferreira et al. 1988; Pietz et al. 1988) and is probably the primary source of reactive oxygen species after reperfusion of ischemic tissues (Saugstad and Aasen 1980).