Depressed Na+-K+-ATPase activity in skeletal muscle at fatigue is correlated with increased Na+-K+-ATPase mRNA expression following intense exercise

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2005-07, Vol.289 (1), p.R266-R274
• Main Authors: Petersen, A. C, Murphy, K. T, Snow, R. J, Leppik, J. A, Aughey, R. J, Garnham, A. P, Cameron-Smith, D, McKenna, M. J
• Format: Article
• Language: English
• Subjects: Adult; Blood Volume; Exercise; Fatigue - enzymology; Female; Humans; Male; Muscle, Skeletal - enzymology; Osmolar Concentration; Potassium - blood; RNA, Messenger - metabolism; Sodium-Potassium-Exchanging ATPase - genetics; Sodium-Potassium-Exchanging ATPase - metabolism; Time Factors
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00378.2004

1 Muscle, Ions and Exercise Group, School of Human Movement, Recreation, and Performance, Centre for Ageing, Rehabilitation, Exercise, and Sport, Victoria University of Technology, and 2 Exercise, Muscle, and Metabolism Unit, School of Health Sciences, Deakin University, Melbourne, Australia Submitted 7 June 2004 ; accepted in final form 13 March 2005 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 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 1 -, 2 -, 3 -, 1 -, 2 - and 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 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 (% 3- O -MFPase rest-fatigue ) ( r = –0.60, P < 0.05). The average postexercise (fatigue, 3 h, 24 h) 1 -isoform mRNA was increased 1.4-fold ( P < 0.05) and approached a significant inverse correlation with % 3- O -MFPase rest-fatigue ( r = –0.56, P = 0.08). Exercise elevated 2 -isoform mRNA at fatigue 2.5-fold ( P < 0.05), which was inversely correlated with % 3- O -MFPase rest-fatigue ( r = –0.60, P = 0.05). The average postexercise 2 -isoform mRNA was increased 2.2-fold ( P < 0.05) and was inversely correlated with the % 3- O -MFPase rest-fatigue ( r = –0.68, P < 0.05). Nonsignificant correlations were found between % 3- 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. Na + -K + pump; signaling; muscle fatigue; ouabain binding Address for reprint requests