Effect of Dose Level on Skeletal Retention of 239 Pu(IV) in the Beagle

Abstract

When /sup 239/Pu(IV) is injected intravenously, its fractional retention in the skeleton of the beagle decreases and then approaches an approximately constant value. The initial fractional deposition of /sup 239/Pu is independent of dose level, but the long term fractional retention is less at the lower dose levels (0.0055 to 0.095 ..mu..Ci/kg) than at the high dose levels (0.30 to 2.9 ..mu..Ci/kg). These findings are in contrast with results on the retention of /sup 239/Pu(IV) in the liver of the beagle. The rate of decrease in hepatic retention of /sup 239/Pu diminishes with decreasing dose level. These opposing effects result from cellular necrosis which is an effect of the ..cap alpha.. irradiation from /sup 239/Pu. Skeletal retention equations are presented for each of the three higher dose levels of /sup 239/Pu and for the group of lower dose levels. These equations and those previously reported for the liver are used to calculate cumulative average radiation doses to the skeleton including marrow, and to the liver throughout the observed lives of the beagles, which were injected in young adulthood at six dose levels of /sup 239/Pu(IV) ranging from 0.016 to 2.9 ..mu..Ci/kg. In the skeletal dose calculations an experimentally determined valuemore » of (7.5 +- 1.0) percent for skeletal weight relative to body weight at injection is used. The concentration of plutonium in plasma has been measured from 1 min to 12.5 years following injection. A sum of four exponentials has been fit to the data. Samples were obtained from dogs at six dose levels, and from well, ill, and terminal dogs.« less