Relative zinc-binding capacity of metallothionein: studies in renal cytosols from zinc-injected rats.

Each rat was injected intraperitoneally once with 0.9% NaCl or zinc (10, 20, 40, or 60 mg zinc/kg b.w.). The zinc content in kidney reached a maximum level of approx. 50 microgram/g kidney, corresponding to a dose (40 mg zinc/kg b.w.). The distribution profiles of the renal cytosols of zinc-injected rats on a Sephadex G-75 column showed that most of the increased zinc was attributable to metallothionein. There was a linear relationship between the zinc contents in cytosol and metallothionein. Our results demonstrated that there was a limit of zinc accumulation in kidneys of zinc-injected rats and that 57% of the increased zinc in renal cytosols was bound to metallothionein. Our results suggest that the role of metallothionein in zinc accumulation in the kidney is similar to that of zinc accumulation in liver.