Pu and Am decorporation in beagles: effects of magnitude of initial Ca-DTPA injection upon chelation efficacy

To investigate the effects of magnitude of initial DTPA injection upon chelation efficacy, five young adult beagles were each given an intravenous injection of 237+239Pu(IV) citrate + 241Am(III) citrate, followed by a single intravenous injection of Ca-DTPA 0.5 hr later. Amounts of this chelating agent administered were 3, 10, 30, 100, and 300 μmole Ca-DTPA/kg body mass. Animals were sacrificed 7 days later. Total-body retention of both plutonium and americium was influenced strongly by the amount of DTPA administered, although the removal of Pu by DTPA was less pronounced than that of Am; and in the range of 30 μmole/kg, an increase of DTPA administration by a factor of 2 resulted in only a 25% decrease in residual body content. Plutonium retention at 7 days was reduced from about 77% in the dog given 3 μmole/kg to 14% in the animal injected with 300 μmole/kg. Corresponding values for americium were 40 and 9%. Also, liver content of both Pu and Am was reduced significantly by larger amounts of administered DTPA, decreasing from 18 to 2% for Pu with increasing levels of DTPA, and from 21 to 1% for Am. If there is a level of Ca-DTPA administration at 30 min after injection in a beagle at which no additional chelation of Pu or Am is produced with increasing dosage, it is greater than 300 μmole/kg. In a 70-kg human, this would be equivalent to the injection of 10 g Ca-DTPA