Excorporation Efficacy with Ca-DTPA of ²⁴¹Am and ²⁵²Cf in the Skeleton, Liver, and Kidney of the Rat and Syrian and Chinese Hamsters Lack of Correlation with the Biological Half-Times

Distribution of intraperitoneally injected ²⁴¹Am- and ²⁵²Cf-citrate in the skeleton, liver, and kidneys at 8 and 71 days after ip injection was investigated in rat and in Syrian and Chinese hamsters. The results confirmed that the most obvious difference of radionuclide metabolism among these animal species is the considerably shorter biological half-time in rat liver (several days) compared to that in livers of Syrian and Chinese hamsters (>100 days). Single injections of Ca-DTPA (diethylenetriamine-pentaacetate) given 24 hr after radionuclides mobilized similar amounts of ²⁴¹Am and ²⁵²Cf from the rat and Chinese hamster livers. In Syrian hamster liver, DTPA effectiveness was markedly lower. On a double logarithmic scale the dose-effect functions for the removal of ²⁵²Cf from liver were linear and, with regard to animal species, parallel to each other. In kidneys, DTPA efficacy increased in the order of rat, Syrian hamster, and Chinese hamster. After 12 Ca-DTPA doses (30 μmoles/kg once weekly, starting 4 days after ²⁵²Cf) chelate efficacy was identical in skeleton of all animal species tested (50% of control removed). From liver and kidneys of Chinese hamster, 94 and 90% of the ²⁵²Cf activity in untreated animals could be mobilized, respectively, whereas DTPA effectiveness was considerably lower in liver and kidneys of rat and Syrian hamster. Thus, no relationship has been established between biological half-lives and availability to DTPA of radionuclides.