Redistribution of cadmium to blood of rats

Abstract

Cd (1 mg/kg iv) is rapidly removed from the blood. By 3 hr after injection the concentration of Cd had decreased almost two orders of magnitude to 46 ng/ml and remained relatively constant for 12 hr before increasing to 75 ng/ml by 60 hr. To determine the mechanism for the increase in blood Cd concentration with time, the distribution of Cd among the blood components was examined at 5 and 60 hr after administration. The concentration of Cd decreased during this time interval by 95% in the plasma, did not change in WBCs, and was increased approximately twofold in RBCs. The concentration of Cd in the ghosts and cytosol of the RBCs increased to the same degree. Examination of the binding of Cd to various RBC cytosolic proteins by Sephadex G-75 chromatography revealed that Cd was bound mainly to high-molecular-weight proteins at both 5 and 60 hr after Cd administration. At 60 hr, a second protein peak with bound Cd was observed which had a molecular weight similar to metallothionein but differed from it in other characteristics. These results suggest that redistribution of Cd to blood is due to the increase in concentration of Cd in the RBCs. This increase does not appear to be solely due to an increase in metal-binding proteins in the cytosol of RBCs.