Transport of uncharged, water-soluble substances (ranging in molecular weight from 180 to 5,000) between the fluid in the peritoneal cavity and plasma was studied in anesthetized female Sprague-Dawley rats. In certain experiments the effect of fluid shifts on the transport was observed by manipulating the effective osmotic pressure or the hydrostatic pressure of the dialysis fluid. Parameters for the distributed model outlined in previous work were obtained from the experimental data for the substances tested. Capillary membrane transport was modeled by pore theory. A single pore radius of 40 A and a pore density of 600 cm-2 were satisfactory. Tissue diffusivities for these substances were found to correspond closely to those in the literature. Additional simulations were performed with a three-compartment model and the results were compared with those of the distributed model.
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