We investigated the relationship between DNA damage detected as single strand breaks using a Comet assay and the expression of glutathione S-transferase P-form(GST-P)as a marker of the early stage of carcinogenesis. In this study, 4-week-old rats were exposed to 10 or 40 ppm diethylnitrosamine(DEN)in drinking water for 14 days, then both DNA damage and GST-P expression were evaluated in the three primary lobes[left(L) , right median(RM)and right anterior(RA) ] of the liver to clarify the

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... tion between two endpoints within the organ over time. Both DNA damage and GST-P expression increased almost in parallel in a dose-and time-dependent manner in all lobes, and those had a good relationship with heterogeneous response, L ≧ RM>RA. Therefore, it was confirmed that the result of the Comet assay could correspond to the histopathological changes appearing in the initiation stage in rat hepatocytes.