Absorption of Lipid and Cholate From Ileal Loops in Unanesthetized Dogs

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Abstract
Oleic acid or triolein, alone or with adjuncts, was introduced every 15 minutes for 3 or 6 hours into the upper end of 24-inch Thiry-Vella ileal loops. The lower fistula drained freely throughout, and after flushing the loops, the amount of lipid which disappeared from the test mixture was determined. The initial concentration of lipid in the test mixture was varied by adding solutions of 0.9% NaCl, 1.0–3.0% NaHCO3, or 0.4–6% desiccated ox bile. The rate of lipid absorption when oleic acid was given varied directly with the initial lipid concentration and inversely with increases in the volume of the test mixture traversing the loop. Since bile salt solutions stimulated loop secretion, lipid absorption rate at given initial oleic acid concentrations decreased. 1.3–2.5% desiccated ox bile, but not higher or lower concentrations, increased the rate of lipid absorption when the initial lipid concentration and the change in volume of test mixture during loop passage were under statistical control. When atropine was given or when NaHCO3 was added to oleic acid, the volume of test material decreased during loop passage and the rate of lipid absorption at given initial oleic acid concentrations increased. The average rate of absorption of undiluted oleic acid in atropinized dogs was 7840 mg/hr. The rate of lipid absorption when triolein was given also increased with the initial triolein concentration, and was augmented further by the administration of atropine. Undiluted triolein in atropinized dogs was absorbed at the average rate of 1690 mg/hr. The rate of cholate absorption increased with the concentration of cholate in the test solution. Oleic acid reduced cholate absorption rate.