Comparative study of the enzymatic defense systems against oxygen-derived free radicals; the key role of glutathione peroxidase

Human WI-38 diploid fibroblasts have been cultivated under high toxic O₂ pressure, and their survival curves are reported. Superoxide dismutase, catalase, or glutathione peroxidase provided some protection when injected in the cells exposed to O₂. This protective effect, recorded after 3 or 4 days of incubation, was the most pronounced when cells were injected just before oxygen exposure. Quantitative injection assays have been performed for the three enzymes. Surprisingly, glutathione peroxidase was found to be much more effective than both catalase and superoxide dismutase, the latter being particularly inefficient.