Abstract: The wide applications of zinc oxide (ZnO) and ubiquitous cadmium (Cd) pollution have increased the risk of humans co-exposure to ZnO and Cd. The synergistic toxicity of bulk ZnO and CdCl2 in mice was investigated. Mice were randomly divided into four groups: a control group and three experimental groups (bulk ZnO, CdCl2, bulk ZnO+CdCl2). Bulk ZnO shows low toxicity in mice. In contrast, CdCl2 causes siginificant damage in the liver indicated by severe liver dysfunction and histopathological abnormalities. Although co-exposure to bulk ZnO and CdCl2 has positive synergistic effects on the uptakes of Zn and Cd in the liver, bulk ZnO can significantly alleviate CdCl2-induced damage in the liver. The bulk ZnO-induced metallothionein synthesis and the inhibition of Cd-induced deprivation of tissue Zn by bulk ZnO might play two key roles in the protective effect of bulk ZnO on CdCl2-induced damage in the liver.

Key words: heavy metal, histopathology, synergistic toxicity, intraperitoneal injection