Superoxide dismutase and pulmonary oxygen toxicity.

The production of superoxide (O2-) under hyperoxic conditions is markedly accentuated leading to the generation of potent oxidants such as hydrogen peroxide (H2O2), hydroxyl radical (HO.), and peroxynitrite (ONOO-). Superoxide dismutase (SOD), by rapidly removing O2-, reduces the tissue concentration of O2- and prevents the production of HO. and ONOO-. Three forms of SOD exist in the lung: CuZnSOD, MnSOD, and extracellular SOD. Considerable supportive, though not all conclusive, evidence suggests that all three forms of SOD are essential for the pulmonary defense against oxygen toxicity, and that enhancement of pulmonary SOD has the potential of protecting against oxygen toxicity.