The gastrointestinal absorption of organically bound forms of plutonium in fed and fasted hamsters

Values of about 0·005-0·01 per cent were obtained for the absorption in fed hamsters of plutonium ingested as Pu⁴⁺ citrate, isocitrate, phytate and malate complexes and Pu³⁺ ascorbate compared with about 0·003-0·004 per cent for Pu⁴⁺ nitrate. Replacing drinking water with tea did not affect the result for Pu⁴⁺ nitrate. Fasting hamsters for 8 h before the administration of plutonium citrate increased absorption to 0·1-0·2 per cent. An extra period of fasting for 4 h after administration did not lead to a further increase in absorption. Similar values were also obtained when plutonium citrate was administered after a 24 h fast, followed either by immediate access to food or a further 4 h fast. In hamsters fasted for 24 h before administration of either Pu³⁺ ascorbate or Pu⁴⁺ nitrate, about 6-7 per cent of the ingested plutonium was retained in the gastrointestinal tract after one week. At three weeks after ingestion of Pu³⁺ ascorbate, gastrointestinal retention had fallen 100-fold without an increase in absorption.