Development of a model for selenite metabolism in humans

The process of building a kinetic model for the metabolism of selenite in humans is described. Plasma, urine and fecal data from a selenium pharmacokinetics study are compared with an a priori model hypothesized before the study was conducted. The reasons for the rejection of the model are given. The iterative process of observing the fit of the model, modifying the model and testing the modification is illustrated by using as examples an intermediate model and a current working model. Several specific problems encountered in trying to fit the a priori and the intermediate model are described along with the approaches taken to resolve them. Finally, some uses of the current model are given, including checking an assumption underlying the pharmacokinetics study, making predictions about the effect of supplementation on plasma levels and developing research leads.