Objectives: This study was conducted to quantitate and compare urinary solute transport by stomach and ileum using an in vivo rat model. Methods: An artificial urine solution was perfused through isolated gastric and ilealsegments in the anesthetized rat. Concentrations of solutes and a volume marker were periodically determined in the perfusate and net solute flux was calculated. Results: The stomach secretes less sodium and very little bicarbonate in comparisonwith ileum. Hydrogen ion and chloride are absorbed by ileum but secreted in large quantities by the stomach. Ammonium, potassium, and urea are absorbed by both segments but to a much lesser degree in the stomach. Overall, there was a net osmolar absorption by ileum, and a net secretion by the stomach. Both segments secrete water to a similar degree. Conclusions: These findings both suggest the mechanism of the hypochloremic metabolicalkalosis seen after urinary reconstruction with the stomach and provide insight into potential therapeutic approaches. Solute fluxes in both the stomach and the ileum are consistent with the known physiology of these segments.
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