The Power of the Comet Assay to Detect Low Level Genotoxicity and DNA Repair Factors Affecting its Power

The comet assay is considered to be a rapid and sensitive procedure for quantitating DNA damage in mammalian cells. In this article, to interpret its outcomes adequately, its power to detect low level genotoxicity and factors affecting its power were reviewed. Although the development of initial lesions into alkali-labile sites and/or SSBs through repairing events is an important factor to support its detecting power, their repair reduce its power to detect SSBs as an initial DNA lesion. The acellular comet assay, in which slides with gel are prepared from untreated cells are exposed after lysis to test agents. Thus, detection of SSBs as initial lesions but not alkali-labile sites generated from DNA lesion such as alkylated bases and the power to detect low level SSBs as initial lesions is lower in the standard than in the acellular assay. The acellular comet assay would be practically used to detect SSBs as initial lesions. The inhibitors of re-synthesis andincisionsteps of the excision repair enhance and suppress comet-tail formation, respectively. Although the incision step of repairing process is necessary to support the sensitivity of the comet assay, its re-synthesis step reduces the power to detect low level genotoxicity. Although this assay can detect a wide variety of genotoxoic compounds and its power to detect genotoxicity were identical to that of the MN test, its power to detect low levels of genotoxic potential is inferior to that of the MN test. However, its power of to detect a low level of genotoxicity can be elevated to a level higher than that of the MN test by using DNA resynthesis inhibitors, such as araC and HU. In conclusion, the outcomes of comet assay should be interpretedappropriately in consideration of the action of DNA repair.