The influence of nutritional deficiencies on gastrointestinal uptake of cadmium and cadmium-metallothionein in rats.

The intestinal uptake and tissue distribution of cadmium (Cd) were studied in control rats and those deficient in zinc (Zn), iron (Fe) or cysteine (SH) using an in situ model where an intestinal loop of 5 cm was incubated with CdCl2 or Cd-MT (MT, metallothionein) for 30 and 60 min. The intestinal content of Cd after incubation with CdCl2 or Cd-MT was not affected by nutritional deficiencies, but the Cd uptake from CdCl2 was always higher than that from Cd-MT. However, both Fe and Zn deficiencies had a marked effect on distribution of Cd in liver, kidney and pancreas. After 30 min incubation in situ with CdCl2, Cd was deposited only in liver in control and SH deficient rats, while Cd was detected also in kidney and pancreas of both Fe and Zn deficient rats. After 60 min incubation with CdCl2, the deposition of Cd in the liver, kidney and pancreas of Fe deficient rat was significantly higher than that in the control. The deposition of Cd after Cd-MT incubation in situ was mainly found in kidney, and nutritional deficiencies increased the tissue deposition of Cd from Cd-MT. Similarly, the renal deposition of Cd absorbed from CdCl2 was markedly increased in Fe deficient rats. These results suggest that the intestinal uptake mechanisms of Cd from CdCl2 and Cd-MT are different and nutritional deficiencies can markedly increase the deposition of Cd in the kidney, the critical organ in chronic cadmium exposure.