Single-fiber expression and fiber-specific adaptability to short-term intense exercise training of Na+-K+-ATPase α- and β-isoforms in human skeletal muscle

• Published in: Journal of applied physiology (1985) 2015-03, Vol.118 (6), p.699-706
• Main Authors: Wyckelsma, V L, McKenna, M J, Serpiello, F R, Lamboley, C R, Aughey, R J, Stepto, N K, Bishop, D J, Murphy, R M
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Adult; Exercise - physiology; Female; Humans; Male; Muscle Fibers, Skeletal - metabolism; Muscle Fibers, Skeletal - physiology; Myosin Heavy Chains - metabolism; Protein Isoforms - metabolism; Sodium-Potassium-Exchanging ATPase - metabolism
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00419.2014

The Na(+)-K(+)-ATPase (NKA) plays a key role in muscle excitability, but little is known in human skeletal muscle about fiber-type-specific differences in NKA isoform expression or adaptability. A vastus lateralis muscle biopsy was taken in 17 healthy young adults to contrast NKA isoform protein relative abundance between type I and IIa fibers. We further investigated muscle fiber-type-specific NKA adaptability in eight of these adults following 4-wk repeated-sprint exercise (RSE) training, comprising three sets of 5 × 4-s sprints, 3 days/wk. Single fibers were separated, and myosin heavy chain (I and IIa) and NKA (α1-3 and β1-3) isoform abundance were determined via Western blotting. All six NKA isoforms were expressed in both type I and IIa fibers. No differences between fiber types were found for α1-, α2-, α3-, β1-, or β3-isoform abundances. The NKA β2-isoform was 27% more abundant in type IIa than type I fibers (P < 0.05), with no other fiber-type-specific trends evident. RSE training increased β1 in type IIa fibers (pretraining 0.70 ± 0.25, posttraining 0.84 ± 0.24 arbitrary units, 42%, P < 0.05). No training effects were found for other NKA isoforms. Thus human skeletal muscle expresses all six NKA isoforms and not in a fiber-type-specific manner; this points to their different functional roles in skeletal muscle cells. Detection of elevated NKA β1 after RSE training demonstrates the sensitivity of the single-fiber Western blotting technique for fiber-type-specific intervention effects.