Comparison between the comet assay and fast micromethod (R) for measuring DNA damage in HeLa cells

The sensitivity and precision of the single cell gel electrophoresis (Comet) assay and Fast Micromethod(R) for DNA damage determinations in human HeLa cell line were compared. The first assay allows analysis of DNA breaks in individual cells while the second is a rapid and convenient procedure for DNA breaks determination in cell suspensions on single microplates. Both assays detect DNA strand breaks, alkali-labile sites and transient breaks occurring at sites of ongoing repair and might be applied for the assessment of surface water genotoxic potential as well as for clinical use. DNA damage in HeLa cells was induced by different doses of gamma-rays generated by Cs-137 (8 to 500 cGy), UV-C light (10 to 1000 J m(-2)) and by different concentrations of 4-nitroquinoline-N-oxide (0.026-2.6 mumol dm(-3)). Gamma rays induced a dose-depended response with the average Comet tail moment values from 7 mm for the negative control to 291 mm for 200 cGy, from 6.1 to 192 mm for 500 J m(-2) of UV-C light and from 7.1 to 238 mm for 1.0 mumol dm(-3) of 4-nitroquinoline-N-oxide. The Fast Micromethod(R) strand scission factor varied from 0.010 for negative control to 0.701 for 500 cGy, from 0.019 to 1.196 for 1000 J m(-2) and from 0.003 to 0.810 for 0.5 mumol dm(-3) of 4-nitroquinoline-N-oxide. Sensitivity was the same for both methods and in the case of 4-nitroquinoline-N-oxide even better precision (lower variation coefficient) was achieved with the Fast Micromethod(R). Since the time required for multiple analysis by the Fast Micromethod(R) is short (2 hours or less), its use in measuring DNA breakage in cells can be recommended for environmental genotoxicity monitoring