Steward, Collene H (2014) Na+,K+-ATPase in human skeletal muscle: the effects of glucose and sodium bicarbonate, and determination of cellular localisation via immunofluorescence. PhD thesis, Victoria University.

Abstract

The sodium-potassium adenosine triphosphatase enzyme (Na+,K+-ATPase; NKA) is a heterodimeric protein comprising catalytic alpha (α-) and regulatory beta (β-) subunits. It drives active coupled transport of Na+ and K+ ions across the plasma membrane of most eukaryotic cells, including skeletal muscle cells, thereby also contributing to regulation of membrane potential. Tight control of Na+/K+ transport and of NKA is essential to maintaining ion homeostasis, excitability and thus muscle function. This thesis comprises two intervention studies investigating different supplementation protocols whose direct or indirect actions target the NKA in skeletal muscle, with the potential to modulate Na+/K+ homeostasis and enhance exercise performance. The first intervention used acute oral glucose supplementation to elevate endogenous insulin, thereby stimulating skeletal muscle NKA activity and modifying K+ homeostasis, under conditions of rest and intense exercise. The second intervention involved chronic sodium bicarbonate ingestion during training, as induced metabolic alkalosis is expected to increase NKA activity in skeletal muscle and lower circulating K+. The third and final study had a methodological focus using immunofluorescence techniques. This study investigated cellular distribution patterns of the NKA isoforms in human skeletal muscle cells and their localisation, contrasting the plasma membrane and intracellular regions, as well as fibre-type differences.

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