| Tricarboxylic acid cycle intermediates in human muscle during prolonged exercise. | |
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MedLine Citation:
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PMID: 2240197 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Seven subjects cycled to fatigue [75 +/- 5 (SE) min] at a work load corresponding to approximately 75% of their maximal oxygen uptake. Biopsies were taken from the quadriceps femoris muscle at rest and during exercise. Muscle glycogen decreased from a preexercise level of 445 +/- 33 mmol glucosyl units/kg dry wt to 50 +/- 14 at fatigue. The sum of the measured tricarboxylic acid cycle intermediates (TCAI = malate + citrate + fumarate + oxaloacetate) was 0.49 +/- 0.05 mmol/kg dry wt at rest, increased to 4.41 +/- 0.23 after 5 min of exercise, and then decreased continuously to 3.33 +/- 0.29 and to 2.83 +/- 0.27 mmol/kg dry wt after 40 min of exercise and at fatigue (P less than 0.05 vs. 5 min), respectively. The point of fatigue was characterized by an enhanced deamination of AMP (judged by increase in IMP) and reduced contents (vs. 5 min of exercise) of lactate, pyruvate, and alanine. In contrast, acetylcarnitine (reflects the availability of acetylunits) increased threefold at the onset of exercise and was maintained approximately at this level until fatigue. It is concluded that prolonged exercise to fatigue at moderate work loads results in glycogen depletion, energy deficiency (increased AMP deamination), reduced levels of three-carbon compounds and TCAI (compared with the initial phase of exercise) but in maintained levels of acetylunits. The present data indicate that carbohydrate depletion may impair aerobic energy production by reducing the level of TCAI. |
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Authors:
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K Sahlin; A Katz; S Broberg |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The American journal of physiology Volume: 259 ISSN: 0002-9513 ISO Abbreviation: Am. J. Physiol. Publication Date: 1990 Nov |
Date Detail:
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Created Date: 1990-12-11 Completed Date: 1990-12-11 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0370511 Medline TA: Am J Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: C834-41 Citation Subset: IM; S |
Affiliation:
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Department of Clinical Physiology, Karolinska Institute, Huddinge University Hospital. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adenine Nucleotides
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metabolism Adult Amino Acids / blood Citric Acid Cycle* Heart Rate Hemoglobins / metabolism Humans Inosine Monophosphate / metabolism Lactates / blood Leg / blood supply Male Muscles / blood supply, physiology* NAD / metabolism Oxidation-Reduction Oxygen Consumption Phosphocreatine / metabolism Physical Exertion* Regional Blood Flow Respiration |
| Chemical | |
Reg. No./Substance:
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0/Adenine Nucleotides; 0/Amino Acids; 0/Hemoglobins; 0/Lactates; 131-99-7/Inosine Monophosphate; 53-84-9/NAD; 67-07-2/Phosphocreatine |
| Comments/Corrections | |
Erratum In:
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Am J Physiol 1995 Jun;268(6 Pt 3):section C followi Am J Physiol 1995 Feb;268(2 Pt 1):section C following table of contents |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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