Radiation Resistance and the CuZn Superoxide Dismutase, Mn Superoxide Dismutase, Catalase, and Glutathione Peroxidase Activities of Seven Human Cell Lines

CuZn superoxide dismutase, Mn superoxide dismutase, catalase, and glutathione peroxidase form the primary enzymic defense against toxic oxygen reduction metabolites in cells. To test the importance of these protective enzymes in the cellular radiation response, the enzymic activities of seven different human cell lines were determined in parallel with their clonogenic survival characteristics. A positive correlation between the content of glutathione peroxidase in cell lines and their extrapolation numbers (n) and quasithreshold doses (<tex-math>$D_{{\rm q}}$</tex-math>) was detected. Between the cellular contents of the other enzymes and D₀, n, and <tex-math>${\rm D}_{{\rm q}}$</tex-math> no positive correlations could be established. An interesting finding was a very high Mn superoxide dismutase content in a malignant mesothelioma cell line P7, which had an extremely high D₀, 5.0 Gy.