Effects of dietary mercury level and cadmium on rat tissue metallothionein: mercury binding and influences on zinc.

Feeding low levels of mercury in diets for rats resulted in its deposition with metallothionein (MT) in the kidney, but not in the liver. The addition of high levels of mercury to diets for rats caused the accumulation of mercury in kidney MT and to a much lesser extent in this low-molecular-weight protein in the liver. The accumulation of mercury in MT also caused zinc to accumulate in it. Treatment of rats with cadmium caused dietary mercury to accumulate in MT in the liver. Feeding stable mercury in the diet caused an increased uptake of labeled mercury in rat kidney MT, but in contrast, caused a decreased content in the liver MT. The mercury proteins from liver and kidney were purified and the amino acid analyses indicated that they are MT. Thus, MT binds low levels of mercury likely to be found in the environment in the kidney but not in the liver.