Changes in arterial, mixed venous and intraerythrocytic ion concentrations during prolonged exercise
Article first published online: 8 NOV 2010
© 2010 EVJ Ltd
Equine Veterinary Journal
Special Issue: Proceedings of the 8th International Conference on Equine Exercise Physiology
Volume 42, Issue Supplement s38, pages 185–190, November 2010
How to Cite
MEYER, N. D., BAYLY, W. M., SIDES, R. H., WARDROP, K. J. and SLINKER, B. K. (2010), Changes in arterial, mixed venous and intraerythrocytic ion concentrations during prolonged exercise. Equine Veterinary Journal, 42: 185–190. doi: 10.1111/j.2042-3306.2010.00189.x
- Issue published online: 8 NOV 2010
- Article first published online: 8 NOV 2010
- [Paper received for publication 13.01.10; Accepted 28.05.10]
- intraerythrocytic ions;
Reasons for performing study: Prolonged equine exercise can cause hypochloraemic alkalosis and hypokalaemia secondary to the loss of hypertonic sweat. Movement of ions in and out of erythrocytes during exercise may help regulate acid-base balance and changes in plasma ion concentrations. The extent to which this happens during prolonged equine exercise has not been reported.
Objectives: To measure changes in blood gases and major plasma and intraerythrocytic (iRBC) ion concentrations of horses undergoing prolonged submaximal exercise.
Methods: Six horses were trotted at ∼30% V̇O2max on a treadmill for 105 min. Arterial (a) and mixed venous (v) blood samples were collected every 15 min, and pre- and post exercise. Blood gases and plasma (pl) concentrations of sodium, potassium, chloride and protein were measured and their iRBC concentrations calculated and compared (P<0.05).
Results: PaCO2 decreased in all horses. pl[Cl-]v decreased and [HCO3-]v increased. Due to the exhalation of CO2 and chloride shifting, [HCO3-]a<[HCO3-]v, pl[Cl-]a>pl[Cl-]v and iRBC[Cl-]a<iRBC[Cl-]v. pl[K+]a and pl[K+]v both initially increased then decreased and horses were hypokalaemic post exercise. Both iRBC[Cl-]a and iRBC[Cl-]v decreased over the course of exercise but there was no change in the arteriovenous difference between them. There was no arteriovenous difference in pl[K+]. iRBC[K +]a>iRBC[K+]v. Conversely, iRBC[Na+]a<iRBC[Na+]v. pl[Na+]a<pl[Na+]v and [TP]a<[TP]v.
Conclusions: Significant arteriovenous differences in iRBC and plasma concentrations of chloride, potassium and sodium reflect the role that movement of ions across erythrocyte cell membranes play in regulating acid-base balance and plasma concentrations of these ions. Exhalation of CO2 has a major influence on this ion flux.