Review, Early Access,
A century of exercise physiology: effects of muscle contraction and exercise on skeletal muscle Na+,K+-ATPase, Na+ and K+ ions, and on plasma K+ concentration-historical developments
Affiliations
- [1] Southwest Univ, Coll Phys Educ, Chongqing, Peoples R China [NORA names: China; Asia, East];
- [2] Victoria Univ, Inst Hlth & Sport, Melbourne, Vic 8001, Australia [NORA names: Australia; Oceania; OECD];
- [3] Zhuhai Coll Sci & Technol, Coll Sports Sci, Zhuhai, Peoples R China [NORA names: China; Asia, East];
- [4] Univ Ottawa, Neuromuscular Res Ctr, Dept Cellular & Mol Med, Ottawa, ON, Canada [NORA names: Canada; America, North; OECD];
- [5] Univ Southern Denmark, Dept Sports Sci & Clin Biomech, Odense, Denmark [NORA names: SDU University of Southern Denmark; University; Denmark; Europe, EU; Nordic; OECD];
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Abstract
This historical review traces key discoveries regarding K+ and Na+ ions in skeletal muscle at rest and with exercise, including contents and concentrations, Na+,K+-ATPase (NKA) and exercise effects on plasma [K+] in humans. Following initial measures in 1896 of muscle contents in various species, including humans, electrical stimulation of animal muscle showed K+ loss and gains in Na+, Cl- and H(2)0, then subsequently bidirectional muscle K+ and Na+ fluxes. After NKA discovery in 1957, methods were developed to quantify muscle NKA activity via rates of ATP hydrolysis, Na+/K+ radioisotope fluxes, [H-3]-ouabain binding and phosphatase activity. Since then, it became clear that NKA plays a central role in Na+/K+ homeostasis and that NKA content and activity are regulated by muscle contractions and numerous hormones. During intense exercise in humans, muscle intracellular [K+] falls by 21 mM (range - 13 to - 39 mM), interstitial [K+] increases to 12-13 mM, and plasma [K+] rises to 6-8 mM, whilst post-exercise plasma [K+] falls rapidly, reflecting increased muscle NKA activity. Contractions were shown to increase NKA activity in proportion to activation frequency in animal intact muscle preparations. In human muscle, [H-3]-ouabain-binding content fully quantifies NKA content, whilst the method mainly detects alpha(2) isoforms in rats. Acute or chronic exercise affects human muscle K+, NKA content, activity, isoforms and phospholemman (FXYD1). Numerous hormones, pharmacological and dietary interventions, altered acid-base or redox states, exercise training and physical inactivity modulate plasma [K+] during exercise. Finally, historical research approaches largely excluded female participants and typically used very small sample sizes.