The gastrointestinal absorption of plutonium and americium in neonatal mammals

Plutonium and americium were administered orally to neonatal guinea pigs as the citrate complexes. The gastrointestinal absorption of both actinides was about 100 - 200 times adult values in one day old animals and decreased over the suckling period to reach adult values by about the time of weaning. It is suggested that a similar pattern of increased absorption should be taken to apply to human neonates with adult values being reached by the time the child is fully weaned. In neonatal guinea pigs given plutonium and americium at up to 10 days of age, retention in the gastrointestinal tract was about 3 - 20% of the ingested dose; in older animals retention was low. It is suggested that doses to the intestinal wall in human neonates could be considerably underestimated if retention is not taken into account, depending on the microdistribution of the retained actinides. Preliminary studies of the chemical form of plutonium in human milk suggest that lactoferrin may be an important binding ligand. 28 refs.; 1 figure; 3 tabs