Identification of 137Cs-and 241Am-binding sites in the oyster Crassostrea gigas

The subcellular distribution and binding of 241Am and 137Cs in the visceral mass of the oyster Crassostrea gigas were investigated following exposure to sea water contaminated with these radionuclides. 241Am was predominantly sequestered by the lysosomal system. Approximately, 10% of 241Am was associated with soluble macromolecules. 241Am was bound to lipofuscin, ferritin and to unidentified ligands of 60 to 15 kdaltons mol. wt. No evidence was found for binding of 241Am to metallothionein synthesized de novo. In contrast, only small amounts of 137Cs were present in lysosomes and 137Cs was not associated with soluble cellular proteins. These results indicate that they enter complete separate metabolic pathways.