Changes in sodium transport in epithelial cells in a rat ileal-augmented bladder model

To investigate changes in the morphology and sodium transport ability of intestinal epithelium diverted to the urinary tract, using an in vitro sodium-binding benzofuran isophthalate (SBFI) technique, as the effects of long-term urine exposure on the transport of electrolytes through intestine are incompletely understood.

Ileal augmentation cystoplasty was conducted in female Sprague-Dawley rats; at 3 and 12 months after surgery the serum concentration of sodium, chloride and potassium were measured. Sodium transport in the ileal epithelial cells diverted to the urinary tract was evaluated using SBFI, as the value of the 340/380 nm excitation ratio measured with fluorescence spectrophotometry. The villous height and the number of villi per ileal length were obtained from haematoxylin and eosin-stained sections.

After 3 months the mean (sd) serum sodium concentrations in normal and augmented rats were 140.4 (2.5) and 140.7 (3.5) mmol/L, respectively; the chloride concentration in normal rats was 97.0 (2.9), and in augmented rats at 3 and 12 months it was 102.4 (2.9) and 99.0 (3.7) mmol/L, respectively. At 3 months, chloride concentrations were significantly higher in augmented than in normal rats (P < 0.05). The mean (sd) 340/380 nm ratio increased by 0.85 (0.09) in the normal ileum, and by 0.73 (0.15) and 0.49 (0.23) in the ileum of augmented rats at 3 and 12 months, respectively; the difference between normal and augmented ileum at 12 months was significant (P < 0.05). At 12 months the villous height in the augmented ileum, at 227.6 (16.0) micro m, was significantly less than in the normal ileum, at 803.4 (66.2) micro m (P < 0.05). However, the number of villi/mm ileum in normal and augmented rats at 12 months was 13.7 (1.5) and 15.0 (0.8), respectively, and not significantly different.

Sodium transport decreased significantly after long-term exposure to urine; the improvement in metabolic change was probably attributable to alterations of electrolyte transport and atrophic changes of the villus.