Document Detail

Plasma hypoxanthine and ammonia in humans during prolonged exercise.
MedLine Citation:
PMID:  10502075     Owner:  NLM     Status:  MEDLINE    
In this study we examined the time course of changes in the plasma concentration of oxypurines [hypoxanthine (Hx), xanthine and urate] during prolonged cycling to fatigue. Ten subjects with an estimated maximum oxygen uptake (VO2(max)) of 54 (range 47-67) ml x kg(-1) x min(-1) cycled at [mean (SEM)] 74 (2)% of VO2(max) until fatigue [79 (8) min]. Plasma levels of oxypurines increased during exercise, but the magnitude and the time course varied considerably between subjects. The plasma concentration of Hx ([Hx]) was 1.3 (0.3) micromol/l at rest and increased eight fold at fatigue. After 60 min of exercise plasma [Hx] was >10 micromol/l in four subjects, whereas in the remaining five subjects it was <5 micromol/l. The muscle contents of total adenine nucleotides (TAN = ATP+ADP+AMP) and inosine monophosphate (IMP) were measured before and after exercise in five subjects. Subjects with a high plasma [Hx] at fatigue also demonstrated a pronounced decrease in muscle TAN and increase in IMP. Plasma [Hx] after 60 min of exercise correlated significantly with plasma concentration of ammonia ([NH(3)], r = 0.90) and blood lactate (r = 0.66). Endurance, measured as time to fatigue, was inversely correlated to plasma [Hx] at 60 min (r = -0.68, P < 0.05) but not to either plasma [NH(3)] or blood lactate. It is concluded that during moderate-intensity exercise, plasma [Hx] increases, but to a variable extent between subjects. The present data suggest that plasma [Hx] is a marker of adenine nucleotide degradation and energetic stress during exercise. The potential use of plasma [Hx] to assess training status and to identify overtraining deserves further attention.
K Sahlin; M Tonkonogi; K Söderlund
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of applied physiology and occupational physiology     Volume:  80     ISSN:  0301-5548     ISO Abbreviation:  Eur J Appl Physiol Occup Physiol     Publication Date:  1999 Oct 
Date Detail:
Created Date:  1999-10-29     Completed Date:  1999-10-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0410266     Medline TA:  Eur J Appl Physiol Occup Physiol     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  417-22     Citation Subset:  IM; S    
Department of Physiology and Pharmacology, Box 5626, Karolinska Institute, Stockholm University College of Physical Education and Sports, S-11486 Stockholm, Sweden.
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MeSH Terms
Adenine Nucleotides / metabolism
Ammonia / blood*
Exercise / physiology*
Heart Rate
Hypoxanthine / blood*
Inosine Monophosphate / metabolism
Lactic Acid / blood
Muscles / metabolism
Oxygen Consumption
Physical Endurance
Uric Acid / blood
Xanthine / blood
Reg. No./Substance:
0/Adenine Nucleotides; 131-99-7/Inosine Monophosphate; 50-21-5/Lactic Acid; 68-94-0/Hypoxanthine; 69-89-6/Xanthine; 69-93-2/Uric Acid; 7664-41-7/Ammonia

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