The effect of pancreatic diversion on lymphatic absorption and esterification of cholesterol in the rat.

Lymph fistula rats with either biliary fistula or pancreaticobiliary fistula were used to measure coenzyme A-independent mucosal cholesterol esterifying activity in the presence and absence of pancreatic exocrine secretion. Efficiency of pancreatic diversion was verified to minimize contamination of mucosal homogenates with adherent luminal enzyme. The synthetic activity of cholesteryl ester hydrolase (E.C. 3.1.1.13) was measured directly in mucosal homogenates. Indirect evidence for mucosal esterifying activity was obtained from hourly cholesteryl ester output into lymph when other factors known to affect cholesterol absorption were controlled. Rats infused intraduodenally at a constant rate with different concentrations of bile salts, polar lipid, and [3H]cholesterol showed that the infused [3H]cholesterol was absorbed and esterified with equal efficiency in the presence and absence of pancreatic flow. Total lymph output of free and esterified endogenous cholesterol was slightly less efficient in the pancreaticobiliary fistula group (85% of bile fistula values) but percent esterification was the same for both groups. Infusion of lipid-free micellar bile salts separately from other bile components produced a highly significant increase in absorption and esterification of lymph cholesterol for both groups. No correlation was found between cholesterol esterifying activity in a) the lumen or b) the mucosa, and cholesteryl ester output into lymph. The present study suggests an alternative enzyme dependent directly or indirectly on the presence of micellar bile salts in the lumen to explain intestinal cholesterol esterifying activity during absorption.