Relative zinc-binding capacity of metallothionein in hepatic cytosols of zinc-injected rats.

In order to determine the zinc-binding capacity of metallothionein in hepatic cytosols of zinc-injected rats, we examined the relationship between zinc contents in cytosols and metallothionein fraction 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 zinc-injected rats on a Sephadex G-75 column showed that the increased zinc was attributable to the metallothionein and high molecular weight proteins. Our results demonstrated that 63% of the increased zinc in hepatic cytosols of zinc-injected rats was bound to metallothionein and that 23% of the increased zinc was bound to high molecular weight proteins. These results suggest that the mechanisms of zinc accumulation in rat liver are different from those of cadmium accumulation.