A biochemical-based model for the dosimetry of dietary organically bound tritium--Part 1: Physiological criteria.
In this paper the physiological criteria for a novel form of model are described whose biokinetics are governed by the overall metabolic reactions of the principal nutrients: carbohydrates, fats, and proteins. The biokinetics of a particular element are based primarily on the oxidation of glucose, fatty acids, and amino acids and the formation of water, carbon dioxide, and urea. The compartmental models proposed follow the pathways of the major elements including hydrogen and, hence, tritium. The parameters for two models of differing complexity--called the HCNO-S and HCNO-C models--were evaluated here on the basis of biochemical reactions; the results of compartmental analysis are reported in an accompanying paper. The simpler form of the HCNO model has single compartments representing the principal nutrients. The more complex model includes compartments representing the longer-term retention of carbohydrates as glycogen, fats as adipose tissue, and proteins in bone and soft tissues. The pool sizes and hydrogen transfer rates are estimated. The incorporation of biochemical reactions and important metabolic parameters serve to give the models a greater semblance of physiological merit than those currently available. For example, ingestion of carbohydrates results in a respiratory quotient of 1.0 and 100% of the hydrogen content oxidized to water, which are the same as values published in the literature. This form of metabolic model enables development of models for other isotopes, besides 3H, of the major elements of the body, e.g., 14C, 15N, 18O.
Richardson
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RB
Radiation Biology and Health Physics Branch, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1J0. richardr@aecl.ca
Dunford
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DW
D000284:Administration, Oral; D004040:Dietary Carbohydrates / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism; D004044:Dietary Proteins / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism*; D005507:Food Contamination, Radioactive / Q000032:analysis*; D006801:Humans; D008657:Metabolic Clearance Rate / Q000502:physiology; D008660:Metabolism / Q000502:physiology; D008954:Models, Biological; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011874:Radiometry / Q000379:methods*; D014316:Tritium / Q000008:administration & dosage / Q000032:analysis* / Q000493:pharmacokinetics*; D014566:Urogenital System / Q000378:metabolism*
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D014316:Tritium