Genotoxicity of bleomycin in human cell lines differing in catalase activity

The influence of catalase on the genotoxic effect of bleomycin (BLM) has been evaluated in three cell lines which differ in catalase activity. CRL1307, cells from Xeroderma pigmentosum patient and CLV102, normal embryonic cells have catalase activity 3.5 and 5 times lower then CRL2088, normal skin fibroblasts. Genotoxicity of BLM (0.5-50 micrograms/ml, 2 h treatment) measured with in vitro micronucleus test did not differ in three tested lines. BLM at concentration range from 1 to 25 micrograms/ml (2 h treatment), tested in comet assay, caused similar degree of DNA damage in CLV102 and CRL2088 cells. Exogenous catalase (300 and 900 u/ml) added to the assay medium with BLM did not influence the micronuclei induction. The absence of endo- and exogenous catalase influence on BLM genotoxicity suggests that not hydrogen peroxide but other reactive oxygen species are formed in reaction of activated BLM with molecular oxygen.