2,4-Diaminotoluene (2,4-DAT)-induced DNA damage, DNA repair and micronucleus formation in the human hepatoma cell line HepG2.

2,4-Diaminotoluene (2,4-DAT) is a widely used industrial intermediate and human exposure is possible in the dye and plastics industries. We investigated the genotoxicity of the environmental pollutant, 2,4-DAT, in human HepG2 cells using the unscheduled DNA synthesis (UDS) test, the micronucleus (MN) assay and single-cell gel electrophoresis (SCGE). 2,4-DAT was first tested by the RNA synthesis inhibition test as a cytotoxicity assay: the IC(50) of 2,4-DAT was 5.2 mM after 20 h of exposure. The compound had a genotoxic effect at concentrations from 1.45 to 6.80 mM in both micronucleus and comet assays. In the micronucleus assay, the number of MN/1000 BNC was 3.5 times higher at a concentration of 6.80 mM 2,4-DAT than in the negative control. At the same concentration, DNA migration (SCGE) showed an Olive tail moment (OTM) of 3.56+/-0.45, as compared to 0.19+/-0.02 for the negative control. The UDS test detected genotoxic effects at lower concentrations than did the other assays (0.01-5 mM). The percentage of cells in repair increased in a concentration-dependent manner to a maximum of 57% at 1mM. At the highest concentration tested (5 mM), the NNG/cell score was 13.6+/-0.5 whereas it was -2.7+/-0.5 for the negative control. These data, based on various endpoints, show a midly genotoxic effect of 2,4-DAT in the HepG2 cells and confirm that this cell line is a suitable model to study the toxic effects of aromatic amines.