BASAL AND MEAL-STIMULATED COLONIC ABSORPTION

PURPOSE: Few quantitative experiments evaluating colonic absorption of water and electrolytes have been performed using an awake, conscious animal model. The purpose of these experiments was to develop this typ e of model and evaluate both basal and meal-stimulated colonic absorpt ion of water and electrolytes. METHODS: Canine Thirty-Vella fistulas w ere created using a 20 cm segment of distal colon under general anesth esia. Colonic absorption studies were performed using infusion of the Thirty-Vella fistulas with a buffer solution containing [C-14]polyethy lene glycol. Electrolyte analysis and concentration of radioactivity i n the effluent were obtained and used to calculate the net flux of wat er, sodium, and chloride. Each study consisted of an one-hour basal pe riod and a three-hour experimental period divided into two groups. Gro up 1 received no meal. Group 2 orally ingested a mixed meal at the com pletion of the basal hour. RESULTS: In the basal state, water and elec trolytes are absorbed from the distal colon at a steady and constant r ate. An orally ingested meal produces a statistically significant incr ease in the rate of absorption, independent of direct colonic luminal contact with the nutrients of the meal given. CONCLUSIONS: These studi es demonstrate an in vivo quantitative and qualitative measure of mamm alian colonic water and electrolyte absorption. An increase in absorpt ion rate occurs in response to a meal that is probably the result of a n unidentified neural or humoral signal.