Effect of replenished lipase on postcibal absorption of fat in a canine model of pancreatic insufficiency.

Clinical studies indicate that as little as 10% of pancreatic secretory capacity is needed to ensure normal digestion; but we found previously that supplying lipase to the postcibal duodenum at > or = 10% of normal rates did not normalize fat absorption in pancreatic insufficiency. Therefore, we examined the dose-response of endogenous lipase on fat absorption. Pancreatic juice was excluded and returned in varied amounts to the postcibal duodenum in dogs with pancreatic fistulas. Meals contained margarine labeled with digestible [14C]triolein and indigestible [3H]glyceroltriether. With an isotope ratio method, we estimated the amount of radiotriolein absorbed hourly from chyme collected for 6 h after a meal from midgut fistulas. When all pancreatic juice was excluded, there was almost no absorption. When 10 or 20% of pancreatic juice was returned, approximately 80% of triolein was absorbed by the midgut, compared with 90% absorption when all pancreatic juice was instilled. However, we observed that at 10 and 20% replenishments, the amount of triolein absorbed in the first hour was much less than in subsequent hours, and thus that absorptive efficiency varied with the fraction of fat emptied from the stomach during the first hour. At rates of 10 or 20% of normal, lipase was equally effective, whether from endogenous juice or exogenous pancreatin.