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Skeletal muscle Na + ‐K + ‐ATPase and K + homeostasis during exercise: effects of short‐term training
Author(s) -
McCUTCHEON L. JILL,
GEOR R. J.,
SHEN HUA
Publication year - 1999
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1999.tb05239.x
Subject(s) - vo2 max , horse , ouabain , chemistry , medicine , endurance training , endocrinology , exercise intensity , zoology , heart rate , sodium , blood pressure , biology , paleontology , organic chemistry
Summary The objective of this study was to determine the effects of 10 consecutive days of moderate intensity training on 1) the concentration of middle gluteal muscle Na + ‐K + ‐ATPase as determined by vanadate‐facilitated [ 3 H]ouabain binding; and 2) plasma potassium regulation before, during and after exercise at 100% of the pre‐training maximum rate of oxygen consumption (V̇ o 2max ). Six mature, unfit Thoroughbred horses completed both incremental (for determination of V̇ o 2max ) and high‐intensity exercise protocols before (HI1) and after (HI2) training. Three additional horses undertook no training or exercise tests and served as controls for determination of middle gluteal muscle Na + ‐K + ‐ATPase concentration. Training consisted of 10 consecutive days of running at 55% V̇ o 2max for 60 min per day (13–14 km/day). For each high intensity exercise protocol, horses completed a 10 min warm‐up at 50% V̇ o 2max , followed by exercise at 100% of pre‐training V̇ o 2max (6° incline, mean speed 9.8 m/s) until fatigue. Training resulted in a 13.8% increase in resting plasma volume (pre: 20.9 ± 0.8 1; post: 23.8 ± 0.9 1; P = 0.03), and an 8.9% increase in V̇ o 2max (pre: 142 ± 4 ml/kg/min; post: 155 ± 4 ml/kg/min; P=0.004) during HI. Peak values for plasma potassium concentration and content during exercise decreased by 13% (P=0.02) and 7% (P = 0.0002), respectively, after training whereas training had no effect on increases in packed cell volume, plasma total solids, and erythrocyte K + concentration and content during exercise. Following training, there was also a significant (23%) increase in Na + ‐K + ‐ATPase concentration in biopsies of middle gluteal muscle, as measured by vanadate‐facilitated [ 3 H]ouabain binding. We conclude that 10 days of moderate intensity exercise results in increases in skeletal muscle Na + ‐K + ‐ATPase and attenuation in the elevation in plasma K + during high intensity exercise at the same absolute workload. The increase in middle gluteal muscle Na + ‐K + ‐ATPase concentration is consistent with decreases in K + efflux from working muscle during exercise.