Superoxide: A New Frontier in Pulmonary Oxygen Toxicity

Although oxygen is necessary for all aerobic life, oxygen at greater than normal air concentrations can be toxic to such life. Pulmonary oxygen toxicity is characterized by irritation, then dyspnea, and finally death if the course is not reversed. Many theories have been advanced to account for the toxicity of hyperoxia, including inactivation of certain enzymes, diversion of metabolic pathways, formation of hydrogen peroxide, promotion of lipid peroxidation, and formation of free radicals. One such free radical is superoxide. Discovery of the catalytic action of superoxide dismutase has expanded insights into oxygen toxicity and holds promise for a means to reduce oxygen's toxic effects. Treatment of rats with superoxide dismutase before exposure to hyperoxia has prevented development of pulmonary oxygen toxicity; use of this enzyme in human pulmonary oxygen toxicity awaits further investigation.