title: Intraenterocyte distribution of absorbed lipid and effects of phosphatidylcholine.
abstract: The present studies were designed to investigate the distribution of absorbed lipid in intestinal mucosal cells and to identify the chylomicron precursor pool. Rats were infused intraduodenally with glyceryl tri[9,10(n)-3H]oleate (135 mumol/h); other rats were in addition infused with 9 mumol/h of phosphatidylcholine. After 5-h infusion the proximal one-half of intestine was removed and the mucosa obtained. It was found that 50% of the radioactivity in the whole homogenate pelleted on centrifugation at 75,000 g.min. The supernatant was further fractionated by high-speed centrifugation resulting in a floating lipid layer, a supernatant, and a microsomal pellet. The results showed that these subcellular fractions had a triacylglycerol specific activity 46-52% of the infusate's specific activity. Including phosphatidylcholine in the duodenal lipid infusion increased the triacylglycerol specific activity of all subcellular fractions (70%) resulting in a specific activity approaching that of the infusate, which would be expected of chylomicron triacylglycerol. These studies demonstrate 1) that considerable mucosal lipid is distributed into a low-speed pellet, 2) that mucosal triacylglycerol specific activity can be greatly increased by including phosphatidylcholine in a lipid infusion, and 3) that despite obtaining multiple subcellular fractions, the chylomicron precursor pool could not be clearly identified in the mucosa of control rats.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: R D
authors.initials: RD
authors.lastname: Parlier
authors.forename: S
authors.initials: S
authors.lastname: Frase
authors.forename: C M
authors.initials: CM
authors.lastname: Mansbach
mesh_terms: D000818:Animals; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008854:Microscopy, Electron; D010713:Phosphatidylcholines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014304:Triolein / Q000378:metabolism*
chemical_list: D010713:Phosphatidylcholines; D014304:Triolein