Subcellular localisation and identification of95mTc- and241Am-binding ligands in the hepatopancreas of the lobsterHomarus gammarus

Following uptake of technetium-95m and americium-241 by lobsters (Homarus gammarus) from food, the subcellular distribution and binding in the major organ of accumulation, the digestive gland, were analysed.^95mTc was predominantly bound to soluble proteins; approximately 40% was bound to two proteins displaying the same elution characteristics as Cdthioneins as indicated by gel permeation and ion-exchange chromatography, indicating reduction and sequestration by metallothionein in vivo. The identity of a third anionic low molecular weight Tc-binding component was not established. No evidence was found for binding of Tc to haemocyanin, ferritin or transferrin. Particulate Tc probably TcO(OH)₂] was bound to plasma membranes and was also present in lysosomes, indicating reduction of pertechnetate and pinocytosis in the digestive gland. In contrast,²⁴¹Am was mainly sequestered by the lysosomal/vacuolar system, indicative of uptake by pinocytosis. Approximately 2 to 3% of the Am was bound to ferritin and 20% was bound to unidentified ligands of 10 and 20 kdaltons mol. wt. There was no evidence for sequestration of Am by metallothionein. These studies prove that waste radionuclides discharged by the nuclear industry are metabolically active and enter the normal metal metabolism and detoxication pathways of a marine shellfish.