Analysis of mutagens with single cell gel electrophoresis, flow cytometry, and forward mutation assays in an isolated clone of Chinese hamster ovary cells

We investigated the induction of DNA strand breaks in the single cell gel electrophoresis (SCGE or comet) assay with whole cell clastogenicity measured with flow cytometric analysis in cells from an isolated clone of the Chinese hamster ovary (CHO) AS52 cell line. Under identical treatment conditions the responses were compared with forward mutation at gpt using 2-acetoxyacetylaminofluorene (2AAAF), ultraviolet radiation (UV) and ethyl methanesulfonate (EMS). Cytotoxicity for each agent was evaluated in the SCGE and forward mutation assays. Forward mutation was 4-10-fold more sensitive than DNA strand breaks detected in the SCGE assay. For 2AAAF and EMS, the kinetics of the induction of genetic damage were similar for the three assays, although there were differences in sensitivity. With UV, the induction kinetics of gpt mutation differed from that expressed by SCGE and flow cytometric analysis. With the chemical mutagens 2AAAF and EMS, there was a high correlation between the SCGE assay and forward mutation and also between the SCGE assay and flow cytometry. There was no significant correlation between flow cytometry and forward mutation. With UV, only the SCGE assay and flow cytometry were correlated. Agent-specific variations in the intragenomic distribution of DNA damage for each mutagen was measured in the SCGE assay.