Association of Americium with Ferritin in the Canine Liver

Abstract

In the canine liver ${}^{241}{\rm Am}({\rm III})$ is distributed ubiquitously at the subcellular level. Significant concentrations were measured in the hepatic connective tissue, the nuclear fraction, the cytosol, the mitochondrial fraction, and the microsomal fraction, and increase in the order given. In the cytosol most of the americium is bound by ferritin. It was also bound by lipofuscin, which was identified histochemically, and by an unidentified material with a molecular weight of 1500. ${}^{241}{\rm Am}\text{-ferritin}$ was isolated in pure form by gel electrophoresis. (Since ferritin that is heavily loaded with iron is found in the microsomal fraction, the high concentration of americium observed in the microsomal fraction could be an anomaly.) The transfer of americium from transferrin to ferritin was shown to occur in vitro as is the case with ${}^{239}{\rm Pu}({\rm IV})$. Partial identification of ${}^{239}{\rm Pu}\text{-ferritin}$ in hepatic cytosol was also achieved. Two concurrent mechanism...