The Retention and Distribution of 241 Am and 65 Zn, Given as DTPA Chelates in Rats and of [ 14 C]DTPA in Rats and Beagles

Abstract

The retention and distribution of /sup 241/Am and /sup 65/Zn, given as the DTPA (diethylenetriaminepentaacetic acid) chelates, were studied in rats for 48 hr following intravenous injection. The retention and distribution of (/sup 14/C)DTPA, injected as the zinc chelate, were determined in rats and two beagles. At 24 hr postinjection (P.I.) rats retained 5% of the /sup 241/Am, 35% of the /sup 65/Zn, and 4% of the (/sup 14/C)DTPA. The loss of these nuclides from blood plasma could be described by the sum of two exponentials, and in rats the respective biological half-lives (t/sub 1/2/) for early times P.I. are t/sub 1/2/ /sup 65/Zn = 1.4 hr, t/sub 1/2/ /sup 241/Am = 0.75 hr, and t/sub 1/2/ (/sup 14/C)DTPA = 0.64 hr; the second component half-times for /sup 241/Am, /sup 65/Zn, and (/sup 14/C)DTPA are 0.2, 6, and 1.6 days, respectively. In beagles the initial t/sub 1/2/ for loss of (/sup 14/C)DTPA from blood was 0.77 hr and the second component t/sub 1/2/ was 4.4 days. The urine was the primary route of excretion in both species. In both rats and dogs, the kidney and liver contained the highest concentration of /sup 241/Am, /sup 65/Zn, and (/sup 14/C)DTPA. The concentrationmore » of /sup 65/Zn in the liver reached a plateau after approximately 4 hr. Significant amounts of /sup 65/Zn, however, were found in the lung, spleen, and femur. In rats the tissue : plasma concentration ratios of (/sup 14/C)DTPA in most organs studied peaked at about 4 hr P.I. In dogs the concentration of (/sup 14/C)DTPA in all soft tissues, except for the brain, exceeded that of plasma at 52 hr P.I. However, in the skeletal parts the concentration was less than in plasma.« less