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Plasma hypoxanthine and ammonia in humans during prolonged exercise.
Dalarna University, School of Health and Social Studies, Medical Science.ORCID iD: 0000-0003-1619-9758
1999 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 80, p. 417-422Article in journal (Refereed) Published
Abstract [en]

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 ( V?O 2max) of 54 (range 47–67) ml?·?kg -1?·?min -1 cycled at [mean?(SEM)] 74?(2)% of V?O 2max 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)?µmol/l at rest and increased eight fold at fatigue. After 60?min of exercise plasma [Hx] was >10?µmol/l in four subjects, whereas in the remaining five subjects it was <5?µmol/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?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.

Place, publisher, year, edition, pages
1999. Vol. 80, p. 417-422
Identifiers
URN: urn:nbn:se:du-2325OAI: oai:dalea.du.se:2325DiVA, id: diva2:519725
Available from: 2006-10-02 Created: 2006-10-02 Last updated: 2017-12-07Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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