EFFECTS OF MACROMOLECULAR CHELATING-AGENTS ON THE RELEASE OF PU-239 AND FE-59 FROM RAT ALVEOLAR MACROPHAGES AFTER PHAGOCYTIC UPTAKE OF PU-239-FE-59-IRON HYDROXIDE COLLOID

The chelation-mediated mobilization of Pu-239 and Fe-59 from rat alveo lar macrophages which had engulfed Pu-239- Fe-59-hydroxide colloids wa s studied by exposing the macrophages to diethylenetriaminepentaacetic acid and macromolecular weight forms of diethylenetriaminepentaacetic acid. The release of Pu-239 and Fe-59 by these macromolecular weight chelating agents and diethylenetriaminepentaacetic acid was assessed i n monolayer culture and shown to be dependent upon the nature of the e ngulfed colloids. Whereas calcium-diethylenetriaminepentaacetic acid, aminoethylcellulose-diethylenetriaminepentaacetic acid, and aminoethyl cellulose-diethylenetriaminepentaacetic acid oxidized with periodic ac id (aminoethylcellulose-diethylenetriaminepentaacetic acid (I-2) exhib ited some effectiveness at releasing Pu-239 and Fe-59 from macrophages which had engulfed the low aggregative colloid, they were less effect ive in the release of these radionuclides from the high aggregative co lloid. The efficacy of these chelating agents on the removal of radion uclides from alveolar macrophages differed between iron and plutonium, suggesting the significant difference in the dissolution and subseque nt metabolism of these radionuclides in alveolar macrophages. From the similarities of the percentage increases in Pu-239 mobilized from the low aggregate colloid by aminoethylcellulose-diethylenetriaminepentaa cetic acid (I-2) and diethylenetriaminepentaacetic acid, it would appe ar that both forms of diethylenetriaminepentaacetic acid could be acce ssing the same deposits of Pu-239; however, for Fe-59 the percentage i ncreases are quite different for the two forms of diethylenetriaminepe ntaacetic acid. SiO2-diethylenetriaminepentaacetic acid, an insoluble macromolecular weight chelating agent, was ineffective at releasing Pu -239 but was slightly effective at releasing radioiron.