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 malabsorptive 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 lymphatic duct cannula, and a duodenal tube. After recovery, a 0.3% lauric acid (C12:0) and 0.37% palmitic acid (C16:0) solution solublized with 3.25 mmol/L lecithin and 23.75 mmol/L taurocholic acid in phosphate-buffered saline was infused at a rate of 3 mL/h via the duodenal tube. After stabilization of lymphatic flow (6 hours), a pulse of radiolabeled lauric and palmitic acid was given via the duodenal tube; absorption was measured by collection of lymphatic fluid and sampling of the portal and jugular venous blood for 4 hours.


RESULTS
The amount of acid recovered in the lymphatics was 51% +/- 6% (mean +/- SD) for lauric and 59% +/- 6% for palmitic. For both fatty acids, < 1% in total was recovered from the portal vein during the 4-hour postbolus period; thereafter, levels in the blood were constant and very low. At necropsy, the majority of the remaining label was found in the intestine.


CONCLUSIONS
These results show no evidence for the preferential absorption of medium-chain fatty acids directly via the portal vein in this model. We suggest that further studies be done to measure directly portal vein absorption of the medium-chain fatty acids.
Sigalet
D L
DL
Department of Surgery, Children's Mercy Hospital, Kansas City, Missouri 64108, USA.
Winkelaar
G B
GB
Smith
L J
LJ
D000042:Absorption; D000818:Animals; D007263:Infusions, Parenteral; D007850:Lauric Acids / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D008208:Lymphatic System / Q000378:metabolism*; D008297:Male; D019308:Palmitic Acid / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D011169:Portal Vein / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D014316:Tritium
D007850:Lauric Acids; D014316:Tritium; C030358:lauric acid; D019308:Palmitic Acid