| Mechanisms of digestion and absorption of dietary vitamin A. | |
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MedLine Citation:
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PMID: 16011460 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Mechanisms involved in the digestion and absorption of dietary vitamin A require the participation of several proteins. Dietary retinyl esters are hydrolyzed in the intestine by the pancreatic enzyme, pancreatic triglyceride lipase, and intestinal brush border enzyme, phospholipase B. Unesterified retinol taken up by the enterocyte is complexed with cellular retinol-binding protein type 2 and the complex serves as a substrate for reesterification of the retinol by the enzyme lecithin:retinol acyltransferase (LRAT). The retinyl esters are then incorporated into chylomicrons, intestinal lipoproteins containing other dietary lipids, such as triglycerides, phospholipids, and free and esterified cholesterol, and apolipoprotein B. Chylomicrons containing newly absorbed retinyl esters are then secreted into the lymph. Although under normal dietary conditions much of the dietary vitamin A is absorbed via the chylomicron/lymphatic route, it is also clear that under some circumstances there is substantial absorption of unesterified retinol via the portal route. Evidence supports the idea that the cellular uptake and efflux of unesterified retinol by enterocytes is mediated by lipid transporters, but the exact number, identity, and role of these proteins is not known and is an active area of research. |
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Authors:
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Earl H Harrison |
Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.; Review |
Journal Detail:
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Title: Annual review of nutrition Volume: 25 ISSN: 0199-9885 ISO Abbreviation: Annu. Rev. Nutr. Publication Date: 2005 |
Date Detail:
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Created Date: 2005-07-13 Completed Date: 2005-09-29 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8209988 Medline TA: Annu Rev Nutr Country: United States |
Other Details:
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Languages: eng Pagination: 87-103 Citation Subset: IM |
Affiliation:
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Human Nutrition Research Center, United States Department of Agriculture, Beltsville, Maryland 20705, USA. harrisoe@ba.ars.usda.gov |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Biological Transport Diet* Digestion* Enzymes / metabolism Esterification Humans Intestinal Absorption* Solubility Vitamin A / administration & dosage, metabolism, pharmacokinetics* |
| Grant Support | |
ID/Acronym/Agency:
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DK44498/DK/NIDDK NIH HHS; HL49879/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Enzymes; 11103-57-4/Vitamin A |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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