Document Detail

Reduced muscle lactate during prolonged exercise following induced plasma volume expansion.
MedLine Citation:
PMID:  9534937     Owner:  NLM     Status:  MEDLINE    
To examine the effects of a dilutional mediated decrease in arterial O2 content on muscle metabolic and substrate behaviour during exercise, plasma volume was acutely expanded by either 14% (LOW) or 21% (HIGH) using a 6% dextran solution dissolved in saline (Macrodex) and compared with a control (CON) condition. The exercise protocol, performed by eight untrained males (VO2max = 45.2 +/- 2.2, X +/- SE) and with the conditions randomized, was conducted for 120 min at 46 +/- 4% VO2max. The content of inosine monophosphate determined on muscle tissue extracted from the vastus lateralis increased (p < 0.05) by 120 min of exercise (0.119 +/- 0.02 vs 0.493 +/- 0.19 mmol/kg dry weight) in CON. No effect of either LOW or HIGH expansion of plasma volume was found. Similarly, phosphocreatine content (mmol/kg dry weight), although reduced (p < 0.05) with exercise, was not different between the conditions at either 3 min (61.9 +/- 3.5, 66.2 +/- 3.5, 64.3 +/- 2.1) or 120 min (52.5 +/- 6.3, 53.8 +/- 5.8, 59.4 +/- 5.5) of exercise. In contrast, both pyruvate and lactate were reduced (p < 0.05) by 3 min of exercise in both LOW and HIGH compared with CON. The reduction in these metabolites with plasma volume expansion was not accompanied by an alteration in glycogen depletion rates. Steady-state VO2 was unaffected by acute hypervolemia. These results suggest that moderate exercise following an approximate 10% reduction in arterial O2 content can be performed without increasing the imbalance between ATP production and utilization rates. Since high energy phosphate transfer and glycolysis appeared not to be increased, mitochondrial respiration was apparently preserved by mechanisms as yet undetermined.
H J Green; S M Grant; S M Phillips; D L Enns; M A Tarnopolsky; J R Sutton
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Canadian journal of physiology and pharmacology     Volume:  75     ISSN:  0008-4212     ISO Abbreviation:  Can. J. Physiol. Pharmacol.     Publication Date:  1997 Dec 
Date Detail:
Created Date:  1998-05-07     Completed Date:  1998-05-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0372712     Medline TA:  Can J Physiol Pharmacol     Country:  CANADA    
Other Details:
Languages:  eng     Pagination:  1280-6     Citation Subset:  IM; S    
Department of Kinesiology, University of Waterloo, ON, Canada.
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MeSH Terms
Exercise / physiology*
Inosine Monophosphate / metabolism
Lactic Acid / metabolism*
Muscles / metabolism*,  physiology
Oxygen Consumption*
Plasma Volume / physiology
Reg. No./Substance:
131-99-7/Inosine Monophosphate; 50-21-5/Lactic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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