FACTORS THAT AFFECT THE PERFORMANCE OF LIPASE ON FAT DIGESTION AND ABSORPTION IN A CANINE MODEL OF PANCREATIC INSUFFICIENCY

In a previous experiment, absorption of [C-14]triolein was poor under low lipase in the first postcibal hour during which luminal conditions change markedly. We wondered how low lipase might be affected by chan ging concentrations of fat, bile salts, titratable acid, pepsin, and f ood particles. Therefore, in dogs with duodenal and midintestinal fist ulas, endogenous bile and pancreatic juice were excluded from the inte stinal lumen and replaced with varied amounts of exogenous bile and pa ncreatic enzymes during steady perfusions. Oil emulsions contained [C- 14]triolein and [H-3]glycerotriether. A double isotope ratio method an d a double isotope, double extraction method were used to determine, r espectively, the amount of [C-14]triolein absorbed and hydrolyzed by t he midgut. Lipolysis increased with both substrate and enzyme inflows, whether inflows were varied by changing concentrations or rates of vo lume flow. But at increasing rates of fat entry, the percent of fat hy drolyzed by the midgut declined. Neither pH 4 nor 5 citrate affected f at hydrolysis or absorption when titratable acid was infused at rates less than or equal to 16 mEq/h; but pepsin reduced both. Whereas meat particles bound lipase, their presence augmented lipolysis. We specula te that rapid gastric emptying of fat and peptic deactivation of duode nal lipase were the main factors responsible for the previously poor p erformance of low lipase in the first postcibal hour.