Subcellular distribution and binding of cadmium to metallothionein in tissues of rainbow trout after exposure to 109Cd in water

Abstract

The uptake and distribution of cadmium in rainbow trout (Salmo gairdneri) was studied after 1 week of exposure to ¹⁰⁹Cd in water and after a subsequent 14‐week period in clean water. The major target organs, that is, gills, kidney, liver and intestine, were analyzed for ¹⁰⁹Cd content and the subcellular distribution of cadmium determined. A successive redistribution of cadmium from the gills and intestine to the liver and kidney was observed. Sephadex G‐75 chromatography of the organs revealed that most of the cadmium was found in the metallothionein‐containing peak and that the amount of cadmium in this peak increased over time after the exposure. Ion‐exchange chromatography on fast protein, polypeptide and polynucleotide liquid chromatography of the metallothionein‐containing peaks revealed that ¹⁰⁹Cd eluted together with copper and polaro‐graphic activity. There was no evidence that other low‐molecular‐weight cadmium‐binding proteins were present in the organs. These results indicate that the metallothionein in rainbow trout binds cadmium after the fish are exposed to the metal in water.