In Vivo Studies on the Interactions of PuIV with Blood Constituents

The distribution of PuIV in blood plasma of beagles was determined as a function of time after injection of PuIV in a citrate buffer solution. The plasma was subjected to gel filtration on G100-G200 columns. Significant amounts of PuIV were found in the region of low-molecular-weight proteins as well as in the molecular weight range of small molecules or ions. The amount of PuIV bound to protein increased during the first few hours after injection, reached a maximum at about 7 hours, and then decreased steadily. Concomitantly the PuIV found in the region of low-molecular-weight compounds decreased continuously from 5 minutes to 30 days. The decrease in the amount of PuIV in the region of low-molecular-weight compounds occurred more rapidly than did the decrease in PuIV associated with low-molecular-weight proteins. The proteins that bound PuIV were identified as transferrin and albumin. These protein-PuIV complexes were separated by ion-exchange chromatography. Their identity was confirmed by electrophoresis and by⁵⁹ Fe labeling. The amount of PuIV bound by transferrin greatly exceeded the amount bound by albumin.