Partial saturation of rat liver Cd-binding proteins by Cd2+ in vivo

Liver Cd-binding proteins (Cd-BP) were isolated from rats chronically treated with 109Cd-labeled CdCl2 for ten days. Fractions purified using Sephadex G-75 and DEAE-Sephadex were characterized and found to be similar to those isolated by other investigators. Cd-binding was not saturated in any of the preparations and significant amounts of Cu and Zn were also found bound to the proteins. The percentage of saturation of Cd-BP1, and Cd-BP2 was independently determined by atomic absorption spectrometry and spectroscopy at 254 nm. These results indicate that the fraction of binding sites unoccupied by Cd on Cd-BP approaches 20% in vivo.