Limitations of zinc and metallothionein accumulation in rat livers following zinc administration.

In order to study whether or not there is a limit of zinc accumulation in livers of zinc-injected rats and establish the biosynthesis relationship of metallothionein by zinc, I examined the accumulated amount of zinc in rat liver after injection of ZnSO4 and the relationship between zinc and metallothionein contents in rat livers. Each rat was injected intraperitoneally once with 0.9% NaCl or zinc (10, 20, 40 or 60 mg zinc/kg b.w.) and was killed 14 h after injection. The distribution profiles of the hepatic cytosols of rats on a Sephadex G-75 column showed that the increased amounts of zinc were attributable to the metallothionein fraction. The zinc content in liver reached a maximum concentration of approx. 125 micrograms/g liver, corresponding to a dose (40 mg zinc/kg b.w.). These data suggested that there was a limit of zinc (essential metal) accumulation in livers of zinc-injected rats. The present results confirmed that the relative induction ability of metallothionein was mainly dependent on the metal content of the liver.