Cell Killing and DNA Damage in Chinese Hamster V79 Cells Treated with Hydrogen Peroxide

Hydrogen peroxide induces lesions in cells similar to those from ionizing radiation, by a Fenton-type production of hydroxyl radicals. At 4 degrees C significant levels of DAN single-strand breaks (ssb) could be measured using the alkaline elution technique, after a 20-min incubation with 10(-5) mol dm-3 H2O2. Only at higher concentrations of H2O2 (greater than 10(-4) mol dm-3) where the levels of ssb measured corresponded to that induced by more than 18 Gy of X-rays, was any significant cell killing detected in a clonogenic assay. Cell killing was observed to coincide with the measurement of significant levels of DNA double-strand breaks (dsb) using the filter elution technique at pH 9.6. This suggests that dsb and not ssb are important as regards hydroxyl-radical-induced cell kill, as found for ionizing radiation. The correlation of induced dsb with lethal events showed that the predicted lethal effect of the H2O2-induced dsb was approximately 5 times less than that of X-ray-induced dsb. This is compared with data previously obtained which showed differences in the lethality of dsb with the quality of radiation (Prise et al. 1987).