Effects of Cadmium and Zinc on Tissue Levels of Metallothionein

Abstract

Although the induced synthesis of metallothionein (MT) after exposure to certain metals has been known for some time, there is little information on the quantitation of MT in various tissues. In this study, tissue MT concentrations were measured by a modified Cd-saturation method in tissues of adult male rats after injection of different metal salts. There were differences in tissue levels of MT, depending on the injected metals. Of all the metals studied, Cd2+ was the most effective element in increasing MT concentrations in liver, kidney, pancreas and small intestine. The highest increase in tissue MT concentration after CdCl2 injection was found in the liver, while the pancreas contained the highest MT level after ZnSO4 injection. Co and Ni salts increased MT levels in both liver and kidney, while Mn and Ca increased MT levels only in liver. A direct correlation between tissue MT levels and Cd or Zn concentration was observed in most of the tissues after injection of CdCl2 or ZnSO4. Although there was no positive relationship between tissue levels of MT and tissue Mn and Ni concentrations, the increase in hepatic Zn after injection of these metals was related to hepatic MT levels. The tissue distribution of injected Cd2+ in control adult rats and Zn-deficient rats was similar. However, there was no increase in pancreatic MT levels in Zn-deficient rats after injection of CdCl2. The high concentration of MT in pancreas after ZnSO4 injection in adult rats and the inability of the pancreas to synthesize MT in Zn-deficient rats suggest that the induction of pancreatic MT synthesis is sensitive to Zn status.(ABSTRACT TRUNCATED AT 250 WORDS)