Measurement of Plasma Metallothionein-I in the Assessment of the Zinc Status of Zinc-Deficient and Stressed Rats

Abstract

These studies were designed to investigate the effects of stress and of changes in zinc status on plasma and liver concentrations of metallothionein-I (MT-I) in rats and to assess the value of plasma MT-I assays in the diagnosis of zinc deficiency. No MT-I was detected by radioimmunoassay in the plasma or liver of rats made hypozincaemic by feeding diets with <1 or 3 mg Zn/kg. Injection of normal rats with endotoxin or CCl4 also decreased plasma zinc levels, but these treatments greatly increased MT-I concentrations in both liver and plasma. Moreover plasma MT-I levels in zinc-deprived rats given endotoxin were only slightly greater than those in untreated rats of normal zinc status. Neither plasma zinc nor MT-I levels were altered in starved rats despite increased levels of the protein in the liver, although a slight increase in plasma MT-I was found in rats pair-fed with zinc-deficient animals. It appears therefore that reduced plasma levels of both zinc and MT-I are indicative of a zinc deficiency state and that assay of plasma MT should be of value in the diagnosis of zinc deficiency.