EFFECT OF REPLENISHED LIPASE ON POSTCIBAL ABSORPTION OF FAT IN A CANINE MODEL OF PANCREATIC INSUFFICIENCY

Clinical studies indicate that as little as 1O% of pancreatic secretor y capacity is needed to ensure normal digestion; but we found previous ly that supplying lipase to the postcibal duodenum at greater than or equal to 10% of normal rates did not normalize fat absorption in pancr eatic insufficiency. Therefore, we examined the dose-response of endog enous lipase on fat absorption. Pancreatic juice was excluded and retu rned in varied amounts to the postcibal duodenum in dogs with pancreat ic fistulas. Meals contained margarine labeled with digestible [C-14]t riolein and indigestible [H-3]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 pa ncreatic juice was excluded, there was almost no absorption. When 10 o r 20% of pancreatic juice was returned, similar to 80% of triolein was absorbed by the midgut, compared with 90% absorption when all pancrea tic juice was instilled. However, we observed that at 10 and 20% reple nishments, the amount of triolein absorbed in the first hour was much less than in subsequent hours, and thus that absorptive efficiency var ied 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.