Further Studies on the Absorption of Actinide Elements from the Gastrointestinal Tract of Neonatal Animals

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Abstract
Pu retention was measured after intragastric administration to neonatal rats, dogs and swine. At 1 wk after adiministration, substantially more of the actinide remained in swine and dogs than in rats. The quantity of 238Pu absorbed by piglets was markedly influenced by such factors as compound solubility, mass of Pu administered, oxidation state of the actinide, and age of the animal at gavage. Cortisone treatment reduced absorption, but was less effective in piglets than in neonatal rats. Measurements of 238Pu transport from ligated segments of the neonatal swine intestine indicated highest absorption from the duodenum, where the actinide was shown, autoradiographically, to be deposited in the epithelial region; in the ileum, deposition was predominantly in the lacteal region. Absorption of actinides by neonatal swine decreased in the order of 233U > 238Pu > 237Np > 244Cm > 241Am. Measurements at 1 yr after gavage showed a much higher retention by swine than by rats.