COPPER DEFICIENCY INCREASES METALLOTHIONEIN-I MESSENGER-RNA CONTENT SELECTIVELY IN RAT-LIVER

A variety of inducers of metallothionein (MT) synthesis have been identified. Copper loading, in particular, has been shown to increase MT expression in the liver and other organs of rodents. In the present study, the effect of severe dietary copper deficiency on MT expression was determined. Weanling rats were fed a purified diet deficient in copper (0.4 mu g/g of diet) or containing adequate copper (5.7 mu g/g of diet) for 4 weeks. Mineral analysis revealed that copper concentrations were severely depressed in the liver, heart, and kidney of the animals fed the copper-deficient diet. The mRNA content for MT-I was markedly increased in the copper-deficient liver bur not in the heart or kidney. The metallothionein protein concentration, however, was not elevated in either liver or heart and was decreased in the kidney of copper-deficient rats. The results demonstrate that copper deficiency enhances MT-I transcription selectively in the liver of rats. It also suggests that copper is nor essential for MT transcription in rats.