Plutonium in Mammals

Abstract

Curremt concepts of Pu metabolism are reviewed. (1) Both the amounts and rates of Pu absorption from the gastrointestinal tract, wound sites, or the lung decrease in the order: soluble complexes > hydrolyzable salts > insoluble compounds. (2) Absorption of Pu from the gastrointestinal tract is greater in very young animals than in adults. Deposition of Pu in bone is greater in growing animals than in young adults.(3) When introduced as a metabolizable complex or simple salt, Pu is transported in plasma chiefly by the iron-transport protein, transferrin. Circulating as the Pu-transferrin complex, Pu is deposited as single atoms in liver parenchymal cells and at the cell-mineral interface of those bone surfaces in dosest proximity to erythropoietic marrow. (4) Liver deposition is favored when Pu is introduced directly into the body by parenteral injection. Skeletal deposition is favored when Pu has been transported across cell barriers as in the case of ingestion or inhalation. (5) In the dog, Pu in hepatic cells is initially associated with soluble ferritin, and later with subcellular structures. Upon the death of hepatic cells, Pu-laden debris accumulates in liver reticuloendothelial (RE) cells. Some of the phagocytized Pu is eventually released from the liver. (6) Concentrations of Pu on bone surfaces are not uniform and decrease in the order: endosteal > periosteal > Haversian. Plutonium concentrations on endosteal surfaces decrease in the order: resorbing > resting

Specific sequestering agents for the actinides. 1. N,N',N'',N'''-Tetra(2,3-dihydroxybenzoyl)tetraazacyclotetra- and -hexadecanes

“…Refluxing 3.4 g (20.5 mmol) of 2,3-dioxomethylenebenzoic in 20 mL of SOCl2 under a Drierite tube for several hours gave a solution, which was evaporated to residue. Coevaporation with benzene (3 X 30 mL) removed traces of excess (4). To 4.55 g (25 mmol) of 2,3-dimethoxybenzoic acid was added I5 mL of SOCl2 and the slurry was stirred at room temperature for 2 h under a Drierite tube.…”

Actinide uptake by transferrin and ferritin metalloproteins

“…Such metal sites participate in the accomplishment of the most essential biological and chemical functions supported by proteins: i) metal homeostasis -uptake, binding and release of metal cations, ii) electron transfer -uptake, storage and release of electrons, iii) catalytic -substrate binding, activation and turnover. Although the various interaction processes between essential cations and proteins are widely studied, focus on the actinide family is more seldom [7][8][9][10]. In particular, the interaction of these cations in the biologically active sites is only partially understood.…”

Actinide-specific sequestering agents and decontamination applications

“…Much larger amounts of Pu(III) and Pu(VI)~ which hydrolyze less readily than Pu(IV) ~ are absorbed. The remainder h)Ydrol)"~es to form an insoluble deposit, which behaves as described above (10,11,27~31 As the liver cells die, the plutonium accumulates in the hemosiderin of the reticulioendothelial cells (10). As in the bone marrow and the liver, plutonium in the spleen and the adrenal glands is also localized with hemosiderin (43,63).…”

“…The - 4 6 concentration of plutonium in plants is 10 to 10-of the surrounding soil ( 23). Further, only 0.03% of ingested Pu(IV) citrate is absorbed by the gastrointestinal tract of mammals, while much smaller amounts of less stable chelates, simple salts, or insoluble compounds of plutonium are absorbed (10,11,13,24). Similarly, insignificant amounts of plutonium.…”

“…Incorporation of plutonium into hemosiderin or the mineral matrix of bone is not permanent, but the mechanisms of release are not known. However, it is more probable that released plutonium will be complexed by transferrin and redeposited instead of ~xcreted (10). In fact, the human iron transport system is so efficient in preventing plutonium excretion that only 20-30% of the plutonium injected into humans was excreted during 27.4 years (12).…”