Induction of Synthesis and Degradation of Metallothionein-I in the Tissues of Rats Injected with Zinc

A radioimmunoassay specific for metallothionein-I (MT-I) has been used for the estimation of this protein in various tissues of the rat following a single intraperitoneal injection of ZnSO4 (2 mg Zn/kg body weight). Quantitative information has also been obtained about the rates of clearance of MT-I from selected tissues following Zn injection. Wide variations were observed in the basal levels of the protein in different tissues of the rat. The levels of MT-I (micrograms/g fresh weight) were high in kidneys (16.9) and testes (14.3), whereas liver (2.4), pancreas (2.2), intestinal mucosa (2.6) and spleen (0.53) contained only small amounts of the protein. MT-I levels in the liver and pancreas increased several fold following Zn injection. The liver had the highest MT-I levels (23.1) at 12 h post-injection, whereas pancreas recorded the highest level (21.6) at 4 h post-injection. The intestinal mucosa registered only a small increase in MT-I; kidneys, spleen and testes were almost unaffected. Concentrations of MT-I returned to the basal levels at 72 h post-injection in all the tissues studied. The biological half-lives of MT-I in the liver, pancreas and mucosa were estimated to be 13.7, 9.8 and 15.0 h respectively.