In vivo genotoxic effect of potassium dichromate in mice leukocytes using comet assay.

Hexavalent chromium is a well-known mutagen and carcinogen. In the present investigation, single-/double-stranded DNA breaks by potassium dichromate (K2Cr2O7) in mice, a sensitive model for genotoxic effects, have been studied in vivo using alkaline single-cell gel electrophoresis (SCGE)/comet assay. Mice were administered orally with a range of doses starting from 0.59 to 76.0 mg/kg body weight of K2Cr2O7 and samples of whole blood were collected at 24, 48, 72, 96 h, week 1 and week 2 post-treatment for alkaline SCGE assay to study DNA damage. The rationale for using leukocytes was to reflect biomarker analysis in humans. Significant increase in mean comet tail length (5.7-24.25 microM) indicating DNA damage was observed at all the doses with K2Cr2O7 when compared with controls (3.26 microM). Maximum increase in mean comet tail length was observed at 9.5 mg/kg body weight at 48 h post-treatment (24.25 microM). The mean comet tail length showed a clear dose-dependent increase from 0.59 to 9.5 mg/kg body weight and a dose-dependent decrease in higher doses (19.0-76.0 mg/kg body weight). A gradual decrease in the tail lengths from 72 h post-treatment was observed by the second week, and values had returned to control levels at all doses, indicating repair of the damaged DNA and/or loss of heavily damaged cells. The study also reveals that comet assay is a sensitive and rapid method for detecting DNA damage caused by heavy metals such as chromium (Cr).