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Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses.
Equine Vet J Suppl. 2006 AugEV

Abstract

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.

Authors+Show Affiliations

Department of Veterinary Clinical Sciences, College of Veterinary Medicine. Washington State University, Pullman, Washington 99164-6610, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

17402435

Citation

Bayly, W M., et al. "Changes in Arterial, Mixed Venous and Intraerythrocytic Concentrations of Ions in Supramaximally Exercising Horses." Equine Veterinary Journal. Supplement, 2006, pp. 294-7.
Bayly WM, Kingston JK, Brown JA, et al. Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses. Equine Vet J Suppl. 2006.
Bayly, W. M., Kingston, J. K., Brown, J. A., Keegan, R. D., Greene, S. A., & Sides, R. H. (2006). Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses. Equine Veterinary Journal. Supplement, (36), 294-7.
Bayly WM, et al. Changes in Arterial, Mixed Venous and Intraerythrocytic Concentrations of Ions in Supramaximally Exercising Horses. Equine Vet J Suppl. 2006;(36)294-7. PubMed PMID: 17402435.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Changes in arterial, mixed venous and intraerythrocytic concentrations of ions in supramaximally exercising horses. AU - Bayly,W M, AU - Kingston,J K, AU - Brown,J A, AU - Keegan,R D, AU - Greene,S A, AU - Sides,R H, PY - 2007/4/4/pubmed PY - 2007/5/3/medline PY - 2007/4/4/entrez SP - 294 EP - 7 JF - Equine veterinary journal. Supplement JO - Equine Vet J Suppl IS - 36 N2 - 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. UR - https://www.unboundmedicine.com/medline/citation/17402435/Changes_in_arterial_mixed_venous_and_intraerythrocytic_concentrations_of_ions_in_supramaximally_exercising_horses_ L2 - https://doi.org/10.1111/j.2042-3306.2006.tb05556.x DB - PRIME DP - Unbound Medicine ER -