DETERMINATION OF THE ROUTE OF MEDIUM-CHAIN AND LONG-CHAIN FATTY-ACID ABSORPTION BY DIRECT MEASUREMENT IN THE RAT

Background: Medium-chain triglycerides are used for the treatment of m alabsorptive states. We measured directly the absorption of medium-and long-chain fatty acids via the mesenteric lymphatics and portal vein in normal animals. These results may be useful in guiding therapy for short-bowel syndrome. Methods: Under anesthesia, male Lewis rats (n=6) underwent placement of jugular and portal venous lines, mesenteric ly mphatic duct cannula, and a duodenal tube. After recovery, a 0.3% laur ic acid (C12:0) and 0.37% palmitic acid (C16:0) solution solubilized w ith 3.25 mmol/L lecithin and 23.75 mmol/L taurocholic acid in phosphat e-buffered saline was infused at a rate of 3 mL/h via the duodenal tub e. After stabilization of lymphatic flow (6 hours), a pulse of radiola beled lauric and palmitic acid was given via the duodenal tube; absorp tion was measured by collection of lymphatic fluid and sampling of the portal and jugular venous blood for 4 hours. Results: The amount of a cid recovered in the lymphatics was 51% +/- 6% (mean +/- SD) for lauri c and 59% +/- 6% for palmitic. For both fatty acids, <1% in total was recovered from the portal vein during the 4-hour postbolus period; the reafter, levels in the blood were constant and very low At necropsy, t he majority of the remaining label was found in the intestine. Conclus ions: These results show no evidence for the preferential absorption o f medium-chain fatty acids directly via the portal vein in this model. We suggest that further studies be done to measure directly portal ve in absorption of the medium-chain fatty acids.