title: 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.
abstract: 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.
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: V L
authors.initials: VL
authors.lastname: Wyckelsma
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and michael.mckenna@vu.edu.au.
authors.forename: M J
authors.initials: MJ
authors.lastname: McKenna
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: F R
authors.initials: FR
authors.lastname: Serpiello
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: C R
authors.initials: CR
authors.lastname: Lamboley
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: R J
authors.initials: RJ
authors.lastname: Aughey
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: N K
authors.initials: NK
authors.lastname: Stepto
authors.affiliation: Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia; and.
authors.forename: D J
authors.initials: DJ
authors.lastname: Bishop
authors.affiliation: Department of Biochemistry, La Trobe University, Melbourne, Victoria, Australia.
authors.forename: R M
authors.initials: RM
authors.lastname: Murphy
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Na+-K+ pump; intermittent exercise training; single fibers