RESUMEN
The retention of 241-Am during the first three months after injection as well as its microdistribution on the 2nd day were investigated in the rat and the Syrian hamster. Deposition, retention and microdistribution in the skeleton of both species are virtually identical; the same holds for kidneys, except for a higher initial deposition in the hamster. The microdistribution of 241-Am in kidneys and liver of both species is homogenous with a distinct accumulation in the cortical zone of the kidneys. A pronounced difference was observed with regard to the elimination of 241-Am from the liver: Most of the 241-Am is excreted by the rat liver with a half time of 7 days whereas this value is about 150 days for the Syrian hamster. The consequences of the species differences are discussed.