Associations of cadmium with zinc and copper in cancer cases and controls

This study was performed in order to search for possible associations between cadmium (Cd) and other metals~ Cd, zinc (Zn), and copper (Cu) levels of renal cortex and liver samples obtained from 196 cancer cases and 198 noncancer controls were analyzed in eight regional institutes in Japan. Cd, Zn, and Cu concentrations in liver and renal cortex of the selected cancer cases were compared to the controls whose localities, age, and sex were matched with the cancer cases. The cancer cases clearly showed higher accumulations of Zn in liver and renal cortex than the noncancer group. Cd showed a similar tendency, but there was no statistical significance between case and control subjects. There was no marked difference in Cu accumulation between the pairs.The best fit regression curve of Zn to Cd on a molar basis in renal cortex was obtained. Curvilinear regression equations of Zn to Cd for both cancer and noncancer groups were drawn. From these two equations, the Zn level of the cancer cases was found to reach a maximum when the Cd level showed 1.4 mmol/kg (157 pxg/g), whereas Zn in the noncancer group peaked at 1.6 mmol/kg (180 Ixg/g) of Cd in renal cortex. This may suggest that excessive Cd accumulation deprives binding sites of Zn in renal cortex when both metals are saturated.