title: Depressed Na+-K+-ATPase activity in skeletal muscle at fatigue is correlated with increased Na+-K+-ATPase mRNA expression following intense exercise.
abstract: We investigated whether depressed muscle Na(+)-K(+)-ATPase activity with exercise reflected a loss of Na(+)-K(+)-ATPase units, the time course of its recovery postexercise, and whether this depressed activity was related to increased Na(+)-K(+)-ATPase isoform gene expression. Fifteen subjects performed fatiguing, knee extensor exercise at approximately 40% maximal work output per contraction. A vastus lateralis muscle biopsy was taken at rest, fatigue, 3 h, and 24 h postexercise and analyzed for maximal Na(+)-K(+)-ATPase activity via 3-O-methylfluorescein phosphatase (3-O-MFPase) activity, Na(+)-K(+)-ATPase content via [(3)H]ouabain binding sites, and Na(+)-K(+)-ATPase alpha(1)-, alpha(2)-, alpha(3)-, beta(1)-, beta(2)- and beta(3)-isoform mRNA expression by real-time RT-PCR. Exercise [352 (SD 267) s] did not affect [(3)H]ouabain binding sites but decreased 3-O-MFPase activity by 10.7 (SD 8)% (P < 0.05), which had recovered by 3 h postexercise, without further change at 24 h. Exercise elevated alpha(1)-isoform mRNA by 1.5-fold at fatigue (P < 0.05). This increase was inversely correlated with the percent change in 3-O-MFPase activity from rest to fatigue (%Delta3-O-MFPase(rest-fatigue)) (r = -0.60, P < 0.05). The average postexercise (fatigue, 3 h, 24 h) alpha(1)-isoform mRNA was increased 1.4-fold (P < 0.05) and approached a significant inverse correlation with %Delta3-O-MFPase(rest-fatigue) (r = -0.56, P = 0.08). Exercise elevated alpha(2)-isoform mRNA at fatigue 2.5-fold (P < 0.05), which was inversely correlated with %Delta3-O-MFPase(rest-fatigue) (r = -0.60, P = 0.05). The average postexercise alpha(2)-isoform mRNA was increased 2.2-fold (P < 0.05) and was inversely correlated with the %Delta3-O-MFPase(rest-fatigue) (r = -0.68, P < 0.05). Nonsignificant correlations were found between %Delta3-O-MFPase(rest-fatigue) and other isoforms. Thus acute exercise transiently decreased Na(+)-K(+)-ATPase activity, which was correlated with increased Na(+)-K(+)-ATPase gene expression. This suggests a possible signal-transduction role for depressed muscle Na(+)-K(+)-ATPase activity with exercise.
authors.affiliation: Muscle, Ions and Exercise Group, School of Human Movement, Recreation and Performance, Centre for Ageing, Rehabilitation, Exercise, and Sport, Victoria University of Technology, PO Box 14428, MCMC, Melbourne, Victoria, Australia 8001.
authors.forename: A C
authors.initials: AC
authors.lastname: Petersen
authors.forename: K T
authors.initials: KT
authors.lastname: Murphy
authors.forename: R J
authors.initials: RJ
authors.lastname: Snow
authors.forename: J A
authors.initials: JA
authors.lastname: Leppik
authors.forename: R J
authors.initials: RJ
authors.lastname: Aughey
authors.forename: A P
authors.initials: AP
authors.lastname: Garnham
authors.forename: D
authors.initials: D
authors.lastname: Cameron-Smith
authors.forename: M J
authors.initials: MJ
authors.lastname: McKenna
mesh_terms: D000328:Adult; D001810:Blood Volume; D015444:Exercise; D005221:Fatigue / Q000201:enzymology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D009994:Osmolar Concentration; D011188:Potassium / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; C045349:3-O-methyl-fluorescein phosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium