Metallothionein and cadmium, zinc and copper distribution in blood of rats.

Plasma and red blood cells were prepared from rats given daily subcutaneous injection of 0.5 mg Cd/kg body weight for 26 weeks. The plasma and hemolysate of the cells were separated by Sephadex G-75 gel filtration. Main cadmium-con-taining (metallothionein) fractions were collected and subjected to DEAE Sephadex A-25 chromatography.DEAE Sephadex A-25 chromatographic profile of the cadmium-containing frac-tion from the plasma showed four cadmium peaks having corresponding copper peaks, but no zinc. DEAE Sephadex A-25 chromatogram of the sample from the hemolysate showed also four cadmium peaks corresponding to the four peaks from the plasma; each peak had an absorption peak at 250 nm. A small amount of zinc was observed at every peak. The separation profiles of two main cadmium peaks of the anion exchange chromatograms from the plasma and hemolysate were consistent with those of two forms of cadmium-induced hepatic and renal metallothionein.These results indicate that the low molecular-weight metal-binding proteins in the blood include metallothionein as a main component and strongly suggest that the proteins affect the turnover of zinc and copper as well as cadmium in the blood.