| Amino acids in the rat intestinal lumen regulate their own absorption from a distant intestinal site. | |
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MedLine Citation:
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PMID: 19541927 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal substrate level. It is not clear, however, whether an amino acid in the intestinal lumen can acutely affect its own absorption from a distant site. Our aim is to study the effect of an amino acid present in rat small intestinal segment on its own absorption from a proximal or distal site and elucidate the underlying mechanisms. The effect of instillation of alanine (Ala) in either jejunum or ileum on its own absorption at ileal or jejunal level was examined in vivo. The modulation of this intestinal regulatory loop by the following interventions was studied: tetrodotoxin (TTX) added to Ala, subdiaphragmatic vagotomy, chemical ablation of capsaicin-sensitive primary afferent (CSPA) fibers, and IV administration of calcitonin gene-related peptide (CGRP) antagonist. In addition, the kinetics of jejunal Ala absorption and the importance of Na+-dependent transport were studied in vitro after instilling Ala in the ileum. Basal jejunal Ala absorption [0.198 +/- 0.018 micromol x cm(-1) x 20 min(-1) (means +/- SD)] was significantly decreased with the instillation of 20 mM Ala in the ileum or in an adjacent distal jejunal segment (0.12 +/- 0.015; P < 0.0001 and 0.138 +/- 0.014; P < 0.002, respectively). Comparable inhibition was observed in the presence of proline in the ileum. Moreover, basal Ala absorption from the ileum (0.169 +/- 0.025) was significantly decreased by the presence of 20 mM Ala in the jejunum (0.103 +/- 0.027; P < 0.01). The inhibitory effect on jejunal Ala absorption was abolished by TTX, subdiaphragmatic vagotomy, neonatal capsaicin treatment, and CGRP antagonism. In vitro studies showed that Ala in the ileum affects Na+-mediated transport and increases K(m) without affecting Vmax. Intraluminal amino acids control their own absorption from a distant part of the intestine, by affecting the affinity of the Na+-mediated Ala transporter, through a neuronal mechanism that involves CSPA and CGRP. |
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Authors:
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Fadi H Mourad; Kassem A Barada; Carmen Khoury; Tamim Hamdi; Nayef E Saadé; Camille F Nassar |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2009-06-18 |
Journal Detail:
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Title: American journal of physiology. Gastrointestinal and liver physiology Volume: 297 ISSN: 1522-1547 ISO Abbreviation: Am. J. Physiol. Gastrointest. Liver Physiol. Publication Date: 2009 Aug |
Date Detail:
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Created Date: 2009-07-22 Completed Date: 2009-08-25 Revised Date: 2009-11-19 |
Medline Journal Info:
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Nlm Unique ID: 100901227 Medline TA: Am J Physiol Gastrointest Liver Physiol Country: United States |
Other Details:
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Languages: eng Pagination: G292-8 Citation Subset: IM |
Affiliation:
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Department of Physiology, American University of Beirut Medical Center, Beirut, Lebanon. fmourad@aub.edu.lb |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Alanine
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administration & dosage,
metabolism* Animals Biological Transport Calcitonin Gene-Related Peptide / metabolism Capsaicin / pharmacology Enteric Nervous System / metabolism Feedback, Physiological Female Ileum / drug effects, innervation, metabolism* Infusions, Intravenous Intestinal Absorption* / drug effects Intestinal Mucosa / drug effects, innervation, metabolism* Jejunum / drug effects, innervation, metabolism* Kinetics Neurons, Afferent / metabolism Proline / metabolism Rats Rats, Sprague-Dawley Reflex Sodium / metabolism Tetrodotoxin / pharmacology Vagotomy Vagus Nerve / metabolism |
| Chemical | |
Reg. No./Substance:
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147-85-3/Proline; 404-86-4/Capsaicin; 4368-28-9/Tetrodotoxin; 56-41-7/Alanine; 7440-23-5/Sodium; 83652-28-2/Calcitonin Gene-Related Peptide |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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