The effect of heavy metal-induced metallothionein on Zn, Cu and Cd accumulation in rat kidney.

To examine the role of metallothionein on heavy metal accumulation in kidneys of rats after Zn, Cd or Cu injection, the relative Zn, Cd or Cu-binding capacity of heavy metal-induced metallothionein in renal cytosol of rats after Zn, Cd or Cu injection was determined. The Zn or Cu increment in renal cytosol after Zn or Cu injection was attributable to low and high molecular weight proteins, while most of the Cd increment was attributable to a low molecular weight protein. The low molecular weight, metal-binding protein was identified as metallothionein using a competitive ELISA. There was a close relationship between heavy metal contents in the renal cytosol and metallothionein of all heavy metal-injected rats. In dose-response and time-course studies, approximately 45, 40 and 85% of the Zn, Cu and Cd increments in renal cytosol were bound to metallothionein after Zn, Cu and Cd injection, respectively. Therefore the order of relative binding capacities of Zn, Cu and Cd-induced metallothionein in kidney was determined to be Cd>Zn approximately Cu. These results suggest that the role of metallothionein in Zn or Cu accumulation in the kidney after Zn or Cu injection is different from that of metallothionein in Cd accumulation in the kidney after Cd injection.