Cadmium-binding proteins in human organs

Cadmium-binding proteins (CdBPs) in the cytosol fractions from several organs of man orally exposed to cadmium (Cd) were examined by gel chromatography. In kidney and liver most of the cadmium (76-87%) in the cytosols was bound to metallothionein, and hepatic metallothionein contained zinc also at a similar level. The pancreas cytosol also contained a metallothionein-like CdBP, although its content was only one-tenth of the hepatic one. In the thyroid gland a prominent CdBP, eluting later than that of metallothionein, was observed; this CdBP was not detectable in normal dogs, pigs, and oxen. No CdBPs were observed in other organs including heart, muscle, genital organs, aorta, and bone. These results suggest that CdBPs participate in accumulation and distribution of cadmium in man, since organs containing CdBP such as kidney, liver, pancreas, and thyroid gland show a tendency to accumulate high levels of cadmium.