OBSERVATION OF THE DYNAMIC DISTRIBUTION OF DIFFERENT FORMS OF ~(111)In IN MICE

The dynamie distribution in mice of three forms of ~(111)In——~(111)In-labelled monoclonall antibody, ~(111)In-DTPA and ~(111)In-citrate (free ~(111)In)——has been studied, ~(111)In-DTPA was eliminated rapidly and the ra- dioactivity was reduced to the background level in all organs in 6 hours (only small amount in the liver and kidneys). The metabolism of free ~(111)In was different from that of ~(111)In-labelled antibody, showing higher elimination rate in the blood than the later although both accumulated in the liver and kidneys. The result suggests that the radioactivity of ~(111)In in the liver is a combined mechanism of metabolism of labelled antibody in the liver and the transportation of free ~(111)In in the blood to the liver. It also shows the possibility of accelerating the elimination of nonspecific radioactivity in the liver with metal chelators.