Comparative evaluation of DNA damage by genotoxicants in primary rat cells applying the comet assay.

Various compounds known to cause DNA damage (hydrogen peroxide, visible light-excited methylene blue, N-nitrosomorpholine and benzo[a]pyrene) were tested with different primary rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) to determine the range of induced DNA damage applying the comet assay. A dose-dependent increase of DNA breaks was observed after treatment with hydrogen peroxide in all cell types studied. The most prominent effect was observed in lymphocytes, whereas only a slight increase of DNA breaks was observed in hepatocytes. Visible light-excited methylene blue caused significant oxidative DNA damage, which did not significantly differ between the cell types used with the exception of hepatocytes, for which a lower level of DNA damage was observed. N-Nitrosomorpholine and benzo[a]pyrene induced a moderate but significant increase of DNA strand breaks in pneumocytes and hepatocytes while in lymphocytes no effect was observed. Our results clearly demonstrate that due to their differential function which is also expressed by the level of drug metabolizing and/or antioxidant enzymes, freshly isolated rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) respond differently to the exposure to genotoxic agents as detected by comet assay.