Document Detail

Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses.
MedLine Citation:
PMID:  17402435     Owner:  NLM     Status:  MEDLINE    
REASONS FOR PERFORMING STUDY: Horses experience major perturbations in acid-base balance during supramaximal exercise. Ion movement in and out of erythrocytes (RBCs) is believed to be important in maintaining acid-base balance but it is unclear as to the extent to which this happens, nor how it affects single measurements of ion concentrations in arterial and venous blood. OBJECTIVES: To clarify the role RBCs play in mitigating perturbations in acid-base balance during high speed exercise in horses, and to describe associated differences in arterial (a) and mixed venous (v) concentrations of key ions. METHODS: Six exercise-trained Thoroughbreds galloped to fatigue at speeds calculated to have an oxygen demand that was 115% of the VO2max. Blood samples (a and v) were collected pre-exercise, during warm-up, at fatigue, and immediately post exercise. Packed cell volume (PCV), pH, PCO2, and plasma concentrations of bicarbonate (HCOP3-), chloride (Cl-), sodium (Na+), potassium (K+), and lactate (Lac-) and strong ion difference (SID) were determined, and RBC concentrations of Lac- and electrolytes calculated for each sample. Data were analysed using a 2-way ANOVA for repeated measures testing for effects of sampling time and site (P<0.05). RESULTS: Plasma and RBC [Cl-] were increased with hypercapnoea and acidaemia. [HCO3-]v was greater than pre-exercise values at fatigue, although [HCO3l]a was lower. Hyperkalaemia and decreased RBC [K+] were evident at fatigue, as was an increased RBC [Na+]. Plasma [K+] started to decrease as soon as exercise ceased and Na+ began to move back onto RBCs in exchange for K+. Concentrations of all measures of Lac- rose from fatigue to post exercise. The SID decreased with exercise and was higher in v at fatigue and post exercise, reflecting the decrease in pH. CONCLUSIONS: RBCs act as a repository for lactate, and therefore the increase in PCV facilitates the maintenance of the muscle to plasma Lac- diffusion gradient during exercise. POTENTIAL RELEVANCE: This serves to keep intramuscular [Lac-] lower than it would otherwise be and, because of the link between Lac- accumulation, pH decrease and the onset of fatigue, may help delay the onset of fatigue.
W M Bayly; J K Kingston; J A Brown; R D Keegan; S A Greene; R H Sides
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Equine veterinary journal. Supplement     Volume:  -     ISSN:  -     ISO Abbreviation:  Equine Vet J Suppl     Publication Date:  2006 Aug 
Date Detail:
Created Date:  2007-04-03     Completed Date:  2007-05-02     Revised Date:  2007-05-18    
Medline Journal Info:
Nlm Unique ID:  9614088     Medline TA:  Equine Vet J Suppl     Country:  England    
Other Details:
Languages:  eng     Pagination:  294-7     Citation Subset:  IM    
Department of Veterinary Clinical Sciences, College of Veterinary Medicine. Washington State University, Pullman, Washington 99164-6610, USA.
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MeSH Terms
Acid-Base Equilibrium / physiology*
Bicarbonates / blood
Blood Chemical Analysis / veterinary
Blood Gas Analysis / veterinary
Carbon Dioxide / blood
Chlorides / blood
Electrolytes / blood*
Erythrocytes / metabolism*
Hematocrit / veterinary*
Horses / blood*
Hydrogen-Ion Concentration
Lactic Acid / blood*
Oxygen Consumption
Physical Conditioning, Animal / physiology*
Potassium / blood
Sodium / blood
Reg. No./Substance:
0/Bicarbonates; 0/Chlorides; 0/Electrolytes; 124-38-9/Carbon Dioxide; 50-21-5/Lactic Acid; 7440-09-7/Potassium; 7440-23-5/Sodium

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

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