Abstract:The effects of CuZn-superoxide dismutase (SOD) on several hydroxyl radical generating systems were studied by using deoxyribose which reacted with hydroxyl radical to release thiobarbituric acid-reactivity compounds. When hydroxyl radical was formed in the Fe3+·O· H2O2 system, its formation was effectively inhibited by SOD, and just slightly inhibited by inactive SOD or bovine serum albudrin (BSA). In Fe(2+)· H2O2 or Cu(2+)· H2O2 system,the hydroxyl radical production was significantly inhibited by BSA. inactive SOD, or SOD which had similar effect to that of inactive SOD. The hydroxyl radical generation from Fe(2+)·O system could be effectively suppressed by inactive SOD or BSA, but not by the "active" SOD which had little effect on hydroxyl radical generation from this system. It is suggested that SOD could affect the hydroxyl radical formation through the following pathways: 1. scavenging superoxide to inhibit Haber-Weiss reaction, 2. chelating metal ions to decrease hydroxyl radical formation; 3. accelerating H2O2 accumulation to enhance hydroxyl radical formation from Fenton reaction.