Fig. 4

Change in % tail DNA in human corneal epithelial cells treated with genotoxic compounds. Human corneal epithelial-transformed (HCE-T) cells were exposed to three compounds (0.5% ethidium bromide, EtBr; 0.5% methyl methanesulfonate, MMS; and 0.001% 4-nitroquinoline 1-oxide, 4-NQO) for 1 min. After treatment, the cells were washed. Fresh culture medium was added, and the cells were further incubated for 2, 4, 6, and 24 h. After incubation, the cells were collected. HCE-T cells were exposed to the test compounds or distilled water as a negative control for 1 min to evaluate DNA damage immediately after exposure (“0 h” or “N.C.” in the figures). Immediately after the treatment, the cells were collected. Comet assay was performed using the collected cell suspensions. Data show the mean ± SD (n = 3). *: Significantly higher than the negative control group at 5% probability level (Dunnett’s multiple comparison test, one-tailed)