title: An age-dependent model for the kinetics of uptake and removal of radionuclides from the G.I. tract.
abstract: An age-dependent model for the transit of radionuclides through the four segments of the G.I. tract is presented. In addition, a compartmental model of the absorption of a large class of radionuclides from the small intestinal contents to the bloodstream is developed. The model includes uptake into the epithelial cells of the gut wall, from which material is lost either by sloughing of cells or passing into the bloodstream. Relevant empirical data are analyzed to provide estimates of values to be assigned to parameters appearing in the model. A marked age dependence in uptake is noted, but this uptake appears to return to adult values at approximately one year in humans. It is suggested that the processes giving rise to the age dependence are brought on by the changing dietary habits of the neonate. Pertinent equations are presented for incorporating future experimental data into the predictions of the model.
mesh_terms: D000328:Adult; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002648:Child; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D011835:Radiation Protection / Q000592:standards; D011868:Radioisotopes; D051381:Rats
chemical_list: D011868:Radioisotopes