The effect of copper on zinc in liver and in metallothionein.

The question as to the increase in Zn and Cu in metallothionein (MT) in response to gold (Au) was examined. Each rat was injected intraperitoneally once with 0.9% NaCl or Au (5, 10 or 20 mg Au/kg b.w.). The Zn content in livers increased in response to Au injection, while the Cu content remained unchanged. After Au injection, 40.0-46.3% of the Au contents and 55.0-60.4% of the Zn contents in livers were detected in cytosol, respectively. The distribution profiles of the hepatic cytosol of Au-injected rats on a Sephadex G-75 column showed that the amount of the increased Zn was ascribable to high molecular weight proteins and MT. The Zn contents in the MT increased in response to Au injection. There was a close relationship between the Zn contents in cytosol and MT. These data demonstrated that 68% of the increased Zn in the hepatic cytosol of Au-injected rats was bound to MT. These results suggest that the role of MT in Zn accumulation in the liver of Au-injected rats was similar to that of MT in Zn accumulation in liver of Zn-injected rats.