In vitro and in vivo genotoxicity assessment of Cr(VI) using comet assay in earthworm coelomocytes

Hexavalent chromium is the major terrestrial pollutant released from electroplating industries, tanneries, thermal power plants and sewage. Cr(VI) is reported genotoxicant in vertebrates. Sub-lethal level of Cr(VI) can cause DNA damage. Earthworms are ecologically important soil invertebrates, used for ecotoxicological studies. In present study coelomocytes of Dichogaster curgensis were used for assessing Cr(VI) genotoxicity using single cell gel electrophoresis [(SCGE) i.e. comet assay] following in vitro and in vivo exposures. Cr(VI) produces reactive oxygen species (ROS) in the cellular system, which can be a major cause of DNA damage. Dose dependent DNA damage was observed during in vitro exposure, while in vivo exposure showed increasing DNA damage till 30 ppm in terms of arbitrary units and unexpected decrease in arbitrary units at 70 and 100 ppm of Cr(VI). It is speculated that the decrease in arbitrary units at higher concentrations might be due to lower DNA mobility, caused by formation of different types of cross-links.