Detection of DNA lesions induced by chemical mutagens using the single-cell gel electrophoresis (Comet) assay .2. Relationship between DNA migration and alkaline condition

The alkaline condition is an important factor for the alkaline single-cell gel electrophoresis (SCG) assay to detect the genotoxic effects of chemicals. In order to understand the relationship between DNA migration and alkaline condition, the effect of 13 model chemical mutagens with different modes of action was evaluated with the alkaline SCG assay under two different alkaline conditions (pH 12.1 and 12.6). CHO cells were sampled just after treatment for 1 h. The X-ray mimetic mutagen BLM increased DNA migration at pH 12.1 and 12.6 and the results were the same at both pH values. Six alkylating mutagens MNU, ENU, MNNG, ENNG, MMS, and EMS and one base adduct inducer 4-NQO induced a dose-dependent response only at pH 12.6. Two DNA crosslinking agents, MMC and DDP, and AMD had negative results. MMC and DDP, however, reduced the positive response of BLM, suggesting that DNA crosslinks could be detected. These results demonstrated that the alkaline condition was important factor for the alkaline SCG assay to detect the genotoxic effects of chemicals. (C) 1997 Elsevier Science B.V.