Tissue metallothionein: dietary interaction of cadmium and zinc with copper, mercury, and silver.

The interaction of dietary Cd and Zn with Cu, Hg, and Ag in relation to tissue metallothionein (MT) was studied with rats. Dietary Cd was found to increase the deposition of Cu and Ag in liver and kidney MT. Cd also caused accumulation of Hg in liver MT but depletion of Hg in kidney MT. In contrast to Cd, high dietary levels of Zn had no influence on the deposition of these metals in MT when they were included in the diet. When Zn was fed in the diet and Cu, Cd, Hg, and Ag were injected into rats, Zn caused increased deposition of these metals in MT, suggesting an interaction at the intestinal level. Hg and Cd were distributed between the two species of MT, but Cu was found predominantly in one of the MT species. Evidence was obtained that Ag was bound to a different MT species than Hg, Cu, or Cd when included in the diet containing Cd.