Document Detail

Tricarboxylic acid cycle intermediates in human muscle during prolonged exercise.
MedLine Citation:
PMID:  2240197     Owner:  NLM     Status:  MEDLINE    
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.
K Sahlin; A Katz; S Broberg
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  259     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1990 Nov 
Date Detail:
Created Date:  1990-12-11     Completed Date:  1990-12-11     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  C834-41     Citation Subset:  IM; S    
Department of Clinical Physiology, Karolinska Institute, Huddinge University Hospital.
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MeSH Terms
Adenine Nucleotides / metabolism
Amino Acids / blood
Citric Acid Cycle*
Heart Rate
Hemoglobins / metabolism
Inosine Monophosphate / metabolism
Lactates / blood
Leg / blood supply
Muscles / blood supply,  physiology*
NAD / metabolism
Oxygen Consumption
Phosphocreatine / metabolism
Physical Exertion*
Regional Blood Flow
Reg. No./Substance:
0/Adenine Nucleotides; 0/Amino Acids; 0/Hemoglobins; 0/Lactates; 131-99-7/Inosine Monophosphate; 53-84-9/NAD; 67-07-2/Phosphocreatine
Erratum In:
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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