Comparison of the localization of chromosome damage induced by calcium chromate and nickel compounds.

Chromosomal aberrations were studied in Chinese hamster ovary cells and in C3H10T1/2 cells following treatment with NiCl2, crystalline NiS, and CaCrO4. All three compounds caused an increase in chromosomal aberrations in a concentration- and time-dependent fashion. The chromosomal aberrations induced by NiCl2 and crystalline NiS occurred predominantly in heterochromatic regions of the chromosomes. Additionally, treatment of cells with crystalline NiS and to a smaller extent long-term treatment with NiCl2 caused a preferential effect on the condensation state of the heterochromatic long arm of the X-chromosome in hamster cells. In contrast, treatment of cells with CaCrO4 did not induce aberrations preferentially in heterochromatin. These results are interesting because nickel(II), which is thought to be the ultimate carcinogen of nickel compounds, binds poorly to DNA, is weakly mutagenic, but induces chromosome damage, probably because of its interaction with nuclear proteins in heterochromatin. Chromate binds to DNA, is mutagenic, and interacts with chromatin randomly.