Cadmium chloride strongly enhances cyclophosphamide-induced chromosome aberrations in mouse bone marrow cells

Earlier we reported that a single 5 mg cadmium chloride (CdCl{sub 2})/kg ip dose enhanced chromosome aberrations (ca) with 50 mg/kg cyclophosphamide (CP) in mouse bone marrow cells. In this report groups of 4 mice were injected ip with saline, 0.31, 0.62, 1.25, 2.5 or 5.0 mg/kg CdCl{sub 2}, followed by saline injections at 24 h. Other mice similarly uninjected at 0 h were injected with 50 mg/kg CP at 24 h. All the mice were injected ip with 4 mg colchicine/kg at 44 h. At 48 h the bone marrow cells were processed for chromosome spreads. After dissection, visual examination revealed obvious internal hemorrhaging of the testes at 1.25 CdCl{sub 2} mg/kg and higher doses. This effect was not further increased by CP treatment. The lowest ca enhancing dose of CdCl{sub 2} on CP was 0.625 mg/kg. Our hypothesis is that Cd replaces zinc presents in numerous DNA repair enzymes and proteins resulting in diminished repair. Subsequently, the excess of unrepaired DNA damage is seen as chromatid breaks, deletions, fragments and exchanges.