Effective Timing of Initial Administration of Ca-DTPA upon Removal of Inhaled Plutonium Nitrate in Rats

The effective timing of an initial injection of Ca-DTPA and a subsequent early treatment on removal of inhaled plutonium nitrate was determined in rats. Plutonium nitrate inhaled rats received an intraperitoneal injection of Ca-DTPA at a daily dose of 150μmol/kg for 3 days, beginning at 0.5, 1, 2, 6, and 12h after inhalation of plutonium; a second regimen studied was injection at a daily dose of 30μmol/kg (the daily recommended dose for humans), beginning at 1h after plutonium inhalation. One group was served as the control with no treatment. During the experiment, the urine and feces were collected every day; on day 4, the rats were sacrificed and dissected to measure plutonium concentration in blood and various organs. The first administration of Ca-DTPA (150μmol/kg) at 1-6h after inhalation initiated an increase in urinary plutonium excretion during the first 24h following inhalation and also resulted in significant increases of urinary plutonium excretion up to 3 days following the treatment. The increase was measured in comparison to the urinary levels of the other two groups that initiated at 0.5h and 12h. In the group that was given 30μmol/kg Ca-DTPA, the high urinary plutonium excretion was found compared to those of the control group; however, these levels were lower than those of the group that was administered a dose of 150μmol/kg. Although the retention rates in the various organs of Ca-DTPA treatment groups varied to the corresponding organs in the control groups, the changed values were very slight. The results indicate that Ca-DTPA administration within 1-6h after exposure to plutonium is effective to increase the urinary excretion of plutonium in rats.