| The ammonium-induced increase in rat brain lactate concentration is rapid and reversible and is compatible with trafficking and signaling roles for ammonium. | |
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MedLine Citation:
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PMID: 17392693 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The glutamate-glutamine shuttle requires a flux of fixed N from neurons to astrocytes. The suggestion that some or all of this N is ammonium has received support from reports that ammonium (as NH(4)(+)) rapidly enters astrocytes. Ammonium might also help control astrocyte energy metabolism by increasing lactate production. If ammonium has these functions, then its effect on brain metabolism must be rapid and reversible. To make a minimal test of this requirement, we have followed the time courses of the changes induced by a 4 min venous infusion of 1 mol/L NH(4)Cl, 2.5 mmol/kg body weight, in rat. Extracellular [NH(4)(+)] in cortex, monitored with ion-selective microelectrodes, reached a peak of approximately 0.7 mmol/L 1.65 mins after the end of the infusion, then recovered. Brain metabolites were monitored non-invasively every 4 mins by (1)H magnetic resonance spectroscopy. Lactate peak area during the 3.2 min acquisition starting at the end of the infusion was 1.84+/-0.24 times baseline (+/-s.e.m., P=0.009, n=9). Lactate increased until 13.2+/-2.1 mins after the end of the infusion and recovered halfway to baseline by 31.2 mins. Glutamate decreased by at least 7.1% (P=0.0026). Infusion of NaCl caused no change in lactate signal. Cerebral blood flow, measured by arterial magnetization labeling, more than doubled, suggesting that the lactate increase was not caused by hypoxia. At least three consecutive ammonium-induced increases in lactate signal could be evoked. The results are compatible with an intercellular trafficking/signaling function for ammonium. |
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Authors:
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Peggy Provent; Nils Kickler; Emmanuel L Barbier; Astrid Bergerot; Régine Farion; Sarah Goury; Païkan Marcaggi; Christoph Segebarth; Jonathan A Coles |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2007-03-28 |
Journal Detail:
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Title: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism Volume: 27 ISSN: 0271-678X ISO Abbreviation: J. Cereb. Blood Flow Metab. Publication Date: 2007 Nov |
Date Detail:
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Created Date: 2007-10-23 Completed Date: 2007-11-19 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8112566 Medline TA: J Cereb Blood Flow Metab Country: United States |
Other Details:
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Languages: eng Pagination: 1830-40 Citation Subset: IM |
Affiliation:
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INSERM, UMR-S 836, Grenoble Institut des Neurosciences, Grenoble, France. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Ammonium Chloride
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pharmacology Animals Astrocytes / metabolism Brain Chemistry / drug effects* Cerebrovascular Circulation / physiology Data Interpretation, Statistical Electrodes, Implanted Extracellular Space / drug effects, metabolism Glutamic Acid / isolation & purification, metabolism Homeostasis / physiology Image Processing, Computer-Assisted Lactic Acid / metabolism* Magnetic Resonance Spectroscopy Male Neurons / metabolism Potassium / metabolism Quaternary Ammonium Compounds / pharmacology* Rats Rats, Wistar Signal Transduction / drug effects, physiology* Sodium Chloride / pharmacology Vascular Resistance / drug effects, physiology Vasodilation / physiology |
| Chemical | |
Reg. No./Substance:
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0/Quaternary Ammonium Compounds; 12125-02-9/Ammonium Chloride; 50-21-5/Lactic Acid; 56-86-0/Glutamic Acid; 7440-09-7/Potassium; 7647-14-5/Sodium Chloride |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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