Comparison of the Localization of Chromosome Damage Induced by Calcium Chromate and Nickel Compounds1

Chromosomal aberrations were studied in Chinese hamster ovary cells and in Oil Id I ' cells following treatment with NiO:, crystalline NiS, and CaCrO«.All three compounds caused an increase in chromosomal aberrations in a concentrationand time-dependent fashion. The chro mosomal aberrations induced by NUI., and crystalline NiS occurred predominantly in heterochromatic regions of the chromosomes. Addition ally, treatment of cells with crystalline NiS and to a smaller extent longterm treatment with N¡( I. 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 CaCrO«did not induce aberra tions 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 heterochrontatin. Chromate binds to DNA, is mutagenic, and interacts with chroma)in randomly.