Abstract
We investigated whether chylomicron formation is involved in the dietary phosphatidylcholine (PC)-induced increase in triglyceride (TG) absorption using an inhibitor of chylomicron formation, pluronic L-81 (L-81). In rats, cannulas were implanted into the duodenum (exps. 1 and 2) and the mesenteric lymph duct (exp. 1), and an emulsified lipid solution containing the test lipids (soybean oil, SO or soybean oil plus phosphatidylcholine, LE) with or without L-81 was infused through a duodenal cannula at a rate 3 ml/h for 2 h, and followed by infusion of a glucose–NaCl solution for 2 h. Mesenteric lymph was collected for 4 h (exp. 1). In exp. 2, the mucosa and contents of the small intestine were collected at 20, 40, or 90 min after the start of duodenal infusion of the test lipid to evaluate accumulation of lipids incorporated into the mucosa in the rats without a lymph cannula. In exp. 1, lymphatic TG outputs rapidly increased with infusion of both test lipids without L-81, but L-81 abolished these increases. TG accumulated in the small intestinal mucosa with L-81 treatment in a time-dependent manner, but the levels of accumulation were similar between the SO and LE groups (exp. 2). There were no differences in the amounts of lipid remaining in the small intestinal lumen between the L-81-treated SO and LE groups. These results indicate that uptake of lipid into the mucosal cells was not increased by LE. We conclude that the formation of chylomicron is responsible for increases in the promotive effect of a high level of dietary PC on the lymphatic absorption of TG.
