Removal of Polymeric Plutonium by DTPA Directed into Cells by Liposome Encapsulation

DTPA (diethylenetriaminepentaacetic acid) encapsulated within lipid spherules (liposomes) removes more plutonium (Pu) from the liver and femurs of mice injected with polymeric Pu than conventional nonencapsulated DTPA. A single intravenous injection, 3 days after Pu injection, of 100 mg/kg of the calcium trisodium salt of DTPA encapsulated in liposomes made with phosphatidylcholine and cholesterol (3:1) reduced the Pu in liver to 43-51% of the control level at 10 days, compared to 60% after injection of nonencapsulated DTPA. It reduced the Pu in the femurs to 60.4-62.5% of the control level, compared to 83-113%. Liposomal DTPA was equally effective when given intraperitoneally, or when stored for 3 days before use. Liposomal DTPA at doses as low as 25 mg/kg was not significantly less effective than a higher dose of 100 mg/kg. Four once-weekly injections of liposomal DTPA continued to give improved removal of Pu compared to conventional DTPA. When given 24 days after Pu, liposomal DTPA had a greater advant...