Plutonium fecal and urinary excretion functions: derivation from a systemic whole-body retention function.

Liver-bile secretion directly influences the content of plutonium in feces. To assess the reliability of plutonium metabolic models and to improve the accuracy of interpreting plutonium fecal data, we developed a compartmental model that simulates the metabolism of plutonium in humans. With this model, we can describe the transport of plutonium contaminants in the systemic organs and tissues of the body, including fecal and urine excretions, without using elaborate kinetic information. The parameter values of the models, which describe the translocation rates and recycling of plutonium in the body, can be derived from a multi-term exponential systemic function for whole-body retention. The analytical derivations and algorithms for solving translocation parameter values are established for the model and illustrated by applying them to the biokinetics and bioassay of plutonium. This study describes how to (1) design a physiological model for incorporating liver biliary secretion and for obtaining a fecal-excretion function, (2) develop an analytical solution for identifying the translocation-parameter values incorporating the recycling of plutonium in the body, and (3) derive a set of urinary and fecal excretion-functions from a published systemic whole-body retention function, generally acknowledged to be accurate, as a real and practical example.