Effects of training on potassium homeostasis during exercise and skeletal muscle Na+,K+-ATPase concentration in young adult and middle-aged Dutch Warmblood horses

Abstract

In horses, the activation of skeletal muscle Na+,K(+)-ATPase during exercise is likely to decrease with age. Training appears to result in an increase in Na+,K(+)-ATPase activity in skeletal muscle with subsequent upregulation of Na+,K(+)-ATPase concentration if the existing Na+,K(+)-ATPase capacity cannot meet requirements.

Effect of show jumping training on the development of locomotory muscle in young horses

“…The Na + ,K + -ATPase content of equine gluteus medius muscle (measured as [ 3 H]ouabain capacity and expressed in pmol/g of wet wt of muscle) in the present study was similar to findings of other studies 31,45 in foals (100 to 200 pmol/g of wet wt of muscle). During postnatal development, an age-dependent decrease in Na + ,K + -ATPase content was detected in the foals of this report, which is in agreement with results of an earlier study 16 in rats and mice.…”

“…23 The Na + ,K + -pump content in equine muscle increases by 20% to 50% with training at different ages, 31,45,47 and it would be likely that the Na + ,K + -pump content would also become upregulated in inexperienced horses by training that starts at 3 years of age. It is known that the initial advantage in jumping technique derived from early training disappears when inexperienced horses also start training.…”

Effects of acute exercise and long-term exercise on total Na+,K+-ATPase content and Na+,K+-ATPase isoform expression profile in equine muscle

“…For the present study, incubations were performed at 37 o C in buffer containing 0.6 µCi/mL of [ 3 H]ouabain i and unlabeled ouabain added to a final concentration of 10 −6 M for 120 minutes under continuous gassing with air. Further processing was performed exactly as described by Suwannachot et al 4,22 On the basis of the specific activity of [ 3 H]ouabain in the incubation medium, the amount of [ 3 H]ouabain taken up and retained in the muscle samples was calculated and after correction (for unspecific uptake, isotopic impurity, and the minute loss of specificially bound [ 3 H]ouabain during the washout) expressed as picomoles per gram of wet weight. 26 Protein concentration-Muscle samples (50 mg) were homogenized by pottering in a 1.5-mL tube in a 1:5 dilution with extraction buffer (25mM Tris-HCl; pH, 6.8; 1% SDS; 5mM EGTA; 50mM NaF; 1mM sodium vanadate; 10% glycerol; and protease inhibitor).…”

“…The Na + ,K + -pump is one of the variables that increase in concentration with increased activity. [2][3][4] The Na + ,K + -pump is a ubiquitous enzyme located in the plasma membrane of the muscle fiber. After an action potential occurs, the pump becomes activated to restore the concentrations of the Na + and K + ions that determine the resting membrane potential,…”

“…[15][16][17][18][19] The Na + ,K + -ATPase content in equine locomotory muscle has been found to increase in several training studies. 3,4,[20][21][22] However, those data were not accompanied by analysis of the different isoforms of Na + ,K + -ATPase via mRNA or protein analysis. Thus, the objective of the study reported here was to determine whether 2 equine muscles located in different regions of the body developed a different response in their Na + ,K + -ATPase content during an exercise-training program; whether Na + ,K + -ATPase isoforms present in other mammalian species are detectable in equine muscle; whether the effect of training on Na + ,K + -ATPase content was associated with a proportional change in mRNA expression and protein production; whether a short exercise bout has an effect on Na + ,K + -ATPase mRNA and protein values; and whether the effect of a short exercise bout on Na + ,K + -ATPase isoforms is still present after training.…”