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.

Binding of 241Am to carp cytosolic fractions in vitro.

Recent studies on the competition between Cd and radionuclides have been reported in marine species. The present investigation aims to study the binding of 241Am to freshwater fish cytosolic fraction before and after Cd-treatment. The main organs studied are the liver, kidneys and muscles. The distribution of americium in the liver cytosol of carp cadmium treated shows a preferential fixation on a 10 KDa fraction with high sulfhydril compounds.

Biodynamic study of americium-241 accumulation in the cytosol of the hepatopancreas of the lobster Homarus gammarus.

In the lobster, most of the radionuclides ingested with contaminated food are concentrated in the digestive gland. Americium-241 accumulation in the hepatopancreas of the lobster was studied during the digestive cycle. Fractionations of cytosols at different times after ingestion of radioactive preys were performed by gel permeation chromatography to determine the distribution of 241Am in the different macromolecular components. 241Am was associated with ferritin during the whole digestive cycle. This observation suggests a correlation between 241Am distribution pathways and iron metabolism. The distribution of 241Am present in the other cytosolic proteins followed two major steps of accumulation which may be correlated to the evolution of the two main cellular types playing an important role in the digestive cycle (B and R type cells).

Chemical behaviour of three radionuclides (cesium, americium and technetium) and their uptake at the cytosolic level in aquatic organisms.

In previous papers, we observed that there were great differences in the subcellular accumulation and elimination of 137Cs, 99Tc and 241Am in different marine animals. In this study, we analysed and compared the behaviour of these radionuclides at the cytosolic level. We found great similarities in the cytosolic distribution of a given radionuclide in the various organisms studied. The chemical characteristics of the radionuclides seem to play a major role in the biochemical affinity and metabolic behaviour in different aquatic organisms.

Distribution of [241Am] in hepato-pancreatic nuclear proteins of the lobster (Homarus gammarus).

Recent studies on the bio-accumulation of transuranic elements in marine invertebrates have demonstrated an intracellular concentration of radionuclides in the digestive gland. The present investigation aims to establish the distribution of [241Am] within the different structures of the cell nucleus. Lobsters were experimentally contaminated through feeding and then killed. The nuclei of hepato-pancreatic cells were isolated, purified and dissociated. The different protein categories were separated in media of increasing ionic strength. The distribution of americium in this material yielded results showing a preferential fixation onto the structural proteins of the nuclear matrix. The radiological consequences of such an affinity are discussed in terms of the life-times of the ligands concerned.