Effect of zinc status of rats on the synthesis and degradation of copper-induced metallothioneins.

Injection of Zn2+-adequate and Zn2+-deficient rats with Cu2+ stimulated the incorporation of l-[35S]cysteine into a low-molecular-weight Cu2+-binding protein in both liver and kidney. No significant incorporation of l-[4,5-3H]leucine into this protein occurred, confirming the previous claim that it was metallothionein and not some other leucine-rich protein. The half-life of the protein was found to be 16.9 +/- 1.0 (S.E.)h in the liver of Zn2+-adequate rats but only 12.3 +/- 0.5h in Zn2+-deficient animals. The degradation rate of the metallothionein was similar to the rate of disappearance of Cu2+ and Zn2+ from the protein, indicating that the release of mental from the protein and its catabolism occurred simultaneously. There was no significant difference in the half-lives of the hepatic or renal copper-thioneins in Zn2+-adequate rats.