Comparison of tissue distribution of cadmium in mice intravenously injected with metallothionein and a polymer of metallothionein.

Polymers of cadmium metallothionein I and II were prepared and used for distribution studies. Mice were intravenously injected with comparable doses of cadmium as chloride, metallothionein and metallothionein-polymer and were killed at 3 h and 24 h after injection. A considerably higher concentration of cadmium was found in the plasma and spleen of animals exposed to metallothionein-polymer than other groups, while the cadmium concentration in the kidney was less than, but in the liver was greater than those injected with cadmium-metallothionein. Gel filtration of liver and kidney cytosols showed that metallothionein is the most stable form of cadmium in the tissues. The injected polymer was degraded into the monomer within 24 h in tissues. The high concentration of polymer in plasma indicates a slow clearance of cadmium in this form. The increased antigenicity of metallothionein-polymer may be related to its slow clearance from blood and increased deposition in spleen.