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This Article Full Text Full Text (PDF) All Versions of this Article: 294/4/E761    most recent 00751.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Green, H. J. Articles by Ouyang, J. PubMed PubMed Citation Articles by Green, H. J. Articles by Ouyang, J.

Dissociation between changes in muscle Na⁺-K⁺-ATPase isoform abundance and activity with consecutive days of exercise and recovery

Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada

Submitted 30 November 2007 ; accepted in final form 25 January 2008

The early plasticity of vastus lateralis Na⁺-K⁺-ATPase to the abrupt onset of prolonged submaximal cycling was studied in 12 untrained participants (O_{2 peak} 44.8 ± 2.0 ml·kg^–1·min^–1, mean ± SE) using a 6-day protocol (3 days of exercise plus 3 days of recovery). Tissue samples were extracted prior to (Pre) and following exercise (Post) on day 1 (E1) and day 3 (E3) and on each day of recovery (R1, R2, R3) and analyzed for changes in maximal protein (β_max) (vanadate-facilitated [³H]ouabain binding), - and β-isoform concentration (quantitative immunoblotting) and maximal Na⁺-K⁺-ATPase activity (V_max) (3-O-methylfluorescein K⁺-stimulated phosphatase assay). For β_max (pmol/g wet wt), an increase (P < 0.05) of 11.8% was observed at R1 compared with E1-Pre (340 ± 14 vs 304 ± 17). For the -isoforms ₁, ₂, and ₃, increases (P < 0.05) of 46, 42, and 31% were observed at R1, respectively. For the β-isoform, β₁ and β₂ increased (P < 0.05) by 19 and 28% at R1, whereas β₃ increased (P < 0.05) by 18% at R2. With the exception of ₂ and ₃, the increases in the isoforms persisted at R3. Exercise resulted in an average decrease (P < 0.05) in V_max by 14.3%. No differences were observed in V_max at E1 - Pre and E3 - Pre or between R1, R2, and R3. It is concluded that 3 days of prolonged exercise is a powerful stimulus for the rapid upregulation of the Na⁺-K⁺-ATPase subunit isoforms. Contrary to our hypothesis, the increase in subunit expression is not accompanied by increases in the maximal catalytic activity.

contractile activity; ion transport; Na⁺-K⁺ pump; adaptation