DNA single-strand breaks and cytotoxicity induced by chromate(VI), cadmium(II), and mercury(II) in hydrogen peroxide-resistant cell lines.

The induction of cytotoxicity and DNA single-strand breaks by chromium(VI), cadmium(II), and mercury(II) were compared in H2O2-resistant Chinese hamster ovary (CHO(R)) cells and parental (CHO(P)) cells. Using a colony-forming assay, CHO(R) cells were found to be significantly more resistant than CHO(P) cells to the cytotoxicity caused by CdCl2 and HgCl2, but not to that caused by Na2CrO4. However, the DNA single-strand breaks produced by each of these metals were significantly lower in the CHO(R) cells. With respect to chromium reduction, the level of chromium(V) in CHO(R) cells was decreased. The role of intracellular active oxygen in the heavy metal-induced DNA damage and cytotoxicity is discussed.