Usage of the standard and modified comet assay in assessment of DNA damage in human lymphocytes after exposure to ionizing radiation

Background. Human organisms are extremely sensitive to ionizing radiation, which has the strong genotoxic effect on the DNA molecule. The aim of the present study was to detect the type of DNA damage and cell death caused by ionizing radiation as well as the sensitivity of the standard and modified comet assay. Methods. The effect of gamma radiation (0.1 Gy and 4 Gy) on human lymphocytes was observed using the standard alkaline and Fpg-modified comet assay with ability to detect oxidized purines as well as with the DNA diffusion test. Results. Parameters of the standard comet assay showed significantly higher values in samples exposed to 4 Gy than in samples exposed to radiation dose of 0.1 Gy and control sample. The Fpg-modified comet assay showed significantly higher values already at dose of 0.1 Gy as the result of oxidative DNA damage. The DNA diffusion test showed that gamma rays lead to apoptosis more often than to necrosis. Conclusions. This observation suggests that the standard alkaline and Fpg-modified comet assays as well as the DNA diffusion test are reliable techniques for estimation of DNA damage and form of the cell death caused by gamma radiation in vitro. In addition Fpg-modified comet assay prove to be more sensitive for detection of gamma irradiation induced DNA damage than the standard assay.