Inorganic cadmium increases the frequency of chemically induced chromosome aberrations in cultured mammalian cells.

The co-clastogenic effect of cadmium ion (Cd2+) was studied in Chinese hamster CHO K1 cells and excision repair-deficient human XP20SSV cells. Cd2+ at < or = 28.0 microM did not show any clastogenic effects under the experimental conditions used. Cd2+ post-treatment at < or = 3.50 microM, however, increased the number of both breakage- and exchange-type chromatid aberrations induced by mitomycin C (MMC) and 4-nitroquinoline 1-oxide (4NQO) in CHO K1 cells. Enhancement of chromosome aberrations induced by MMC was observed when CHO K1 cells were treated with Cd2+ during the G1 phase. Cd2+ was also co-clastogenic with MMC in XP20SSV cells. Its co-clastogenic effect, however, was not observed in 4NQO-treated XP20SSV cells. These results suggest that Cd2+ inhibits DNA pre-replicational repair, perhaps DNA excision repair, thereby causing co-clastogenic effects.