Site specificity and meal stimulation of the intestinal absorption of water, electrolytes, and bile acids.

Ileal water and electrolyte absorption exceed jejunal absorption in both the basal and meal-stimulated states. The purposes of these experiments were to determine: (1) if luminal bile acids alter basal or meal-stimulated intestinal absorption, and (2) if there is site specificity or meal stimulation of intestinal bile acid absorption. Twenty-five centimeters of canine proximal jejunal and distal ileal Thiry-Vella fistulas were constructed. Simultaneous jejunal and ileal absorption studies (n = 88) were performed with a luminal perfusate containing polyethylene glycol labeled with radioactive carbon-14 to calculate the absorption of water, electrolytes, and the bile acid taurocholate (TC). In group 1, there was no TC in the luminal perfusate, whereas in group 2, 10 mM of TC was present in the luminal perfusate. Half of the observations were performed after a meal stimulus, which consisted of an orally ingested, 480-kcal mixed nutrient meal. Intraluminal TC did not affect basal or meal-stimulated water or electrolyte absorption. In both the basal and meal-stimulated states, ileal absorption of water, electrolytes, and TC significantly exceeded jejunal absorption (p < 0.05). A meal significantly stimulated water and electrolyte absorption in both the jejunum and ileum, but it stimulated absorption of TC in the ileum only (p < 0.05). Intraluminal TC does not alter basal or meal-stimulated intestinal water and electrolyte absorption. A meal stimulates increased water and electrolyte absorption in both the jejunum and the ileum, but it stimulates bile acid absorption in the ileum only. Bile acid absorption is site specific and responsive to a meal stimulus.