INTERCONNECTED-TUBES MODEL OF HEPATIC ELIMINATION

The distributed-tubes model of hepatic elimination is extended to incl ude intermixing between sinusoids, resulting in the formulation of a n ew, interconnected-tubes model. The new model is analysed for the simp le case of two interconnected tubes, where an exact solution is obtain ed. For the case of many strongly-interconnected tubes, it is shown th at a zeroth-order approximation leads to the convection-dispersion mod el. As a consequence the dispersion number is expressed, for the first time, in terms of its main physiological determinants: heterogeneity of flow and density of interconnections between sinusoids. The analysi s of multiple indicator dilution data from a perfused liver preparatio n using the simplest version of the model yields the estimate 10.3 for the average number of interconnections. The problem of boundary condi tions for the dispersion model is considered from the viewpoint that t he dispersion-convection equation is a zeroth-order approximation to t he equations for the interconnected-tubes model. (C) 1997 Academic Pre ss Limited.