Electrolyte transport in rat colon: comparative effects of intestinal resections and bypass

In the present study the influence of different types of intestinal resection (50% distal and 50% proximal small bowel resection) and bypass (50% jejunoileal bypass) upon water and electrolyte (Na and K) colonic transport was examined. Four weeks after resections and bypasses no significant changes in wet and dry tissue weights, serum sodium and potassium values were found in comparison to sham-operated controls. In vivo net absorption of sodium, measured in micromoles of 22Na+ which disappeared from the medium during a determined period (15, 30, 45 and 60 min), in sham-operated animals, showed a gradual increase with the increase in the perfusion time, rising from 144 +/- 20 mumol at 15 min of perfusion to 425 +/- 28 mumol at 60 min. One month after the resection, Na absorption, expressed as total absorption and as micromoles per square centimeter, was not significantly modified in animals distally and proximally resected, but did significantly increase in bypassed rats with respect to sham-operated animals. When the results were calculated taking into account the tissue wet weight, the values of the resected rats continued to show no modifications; however, there was a compensation in the bypassed rats. These data demonstrate that the increase in the absorptive capacity of the colon in bypassed rats is due to morphological changes, which could originate from the trophic influence of enteroglucagon or from the effect of the secretions which flowed directly into the colon from the blind loop, an action which does not occur in resected rats. The effects of resection and bypass upon K+ colonic secretion showed no significant differences among the groups studied.(ABSTRACT TRUNCATED AT 250 WORDS)