Effects of ingestion of cadmium-polluted rice or low-dose cadmium-supplemented diet on the endogenous metal balance in female rats

The concentrations of endogenous metal ions in liver, kidney, and bone tissues of female rats were measured after ingestion of cadmium-polluted rice (1.24 ppm as Cd) or cadmium-supplemented rice (1.24 and 4.96 ppm) for 2 or 4 mo. The metal accumulated mainly in the kidneys and in the liver. The concentration of cadmium (Cd) in the kidneys of rats fed a 1.24-ppm Cd-supplemented diet was significantly higher than in the Cd-polluted rice group. After 2 mo, the levels of iron and sodium in the liver were elevated in the Cd-polluted rice group, but not in the 1.24-ppm Cd-supplemented group, as compared to controls. The zinc concentration in the Cd-polluted rice group was decreased. The concentration of copper in the kidneys was increased for all Cd-containing diet groups. After 4 mo, the effects of Cd on essential metals in the Cd-polluted and 1.24-ppm Cd-supplemented groups had almost disappeared, although several metal ions in selected organs in the 4.96-ppm Cd-supplemented group showed more prominent changes than in the group exposed for 2 mo. These results suggest that the effects of short-term exposure to Cd on essential metal balance are stronger for rice-bound Cd than for inorganic Cd, although the absorption rate of Cd in Cd-polluted rice may be lower than that of cadmium chloride added to rice.