Inhibition of the genotoxicity of bleomycin by superoxide dismutase

Bleomycin was found to be cytotoxic and mutagenic in the CHO/HGPRT forward mutation assay. Approximately 50% cell mortality was achieved after a 1-h exposure to 10 micrograms/ml BLM. Bleomycin was also found to induce mutation to thioguanine resistance in a dose-dependent manner. Both the cyto- and geno-toxicity resulting from BLM exposure could be reduced by the prior addition of superoxide dismutase, implicating a role for activated oxygen metabolites in the mechanism of toxicity of bleomycin.