HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 586/5/1447    most recent jphysiol.2007.143073v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nordsborg, N. Articles by Bangsbo, J. PubMed PubMed Citation Articles by Nordsborg, N. Articles by Bangsbo, J. Related Collections Skeletal Muscle and Exercise

¹ Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen, Denmark

The effect of dexamethasone on Na⁺,K⁺ pump subunit expression and muscle exchange of K⁺ during exercise in humans was investigated. Nine healthy male subjects completed a randomized double blind placebo controlled protocol, with ingestion of dexamethasone (Dex: 2 x 2 mg per day) or placebo (Pla) for 5 days. Na⁺,K⁺ pump catalytic 1 and 2 subunit expression was 17% higher (P < 0.05) and the structural β1 and β2 subunit expression was 6–8% higher (P < 0.05) after Dex compared with Pla. During one-legged knee-extension for 10 min at low intensity (LI; 18.6 ± 1.0 W), two moderate intensity (51.7 ± 2.4 W) exercise bouts (MI₁: 5 min; 2 min recovery; MI₂: exhaustive) and two high-intensity (71.7 ± 2.5 W) exercise bouts (HI₁: 1 min 40 s; 2 min recovery; HI₂: exhaustive), femoral venous K⁺ was lower (P < 0.05) in Dex compared with Pla. Thigh K⁺ release was lower (P < 0.05) in Dex compared with Pla in LI and MI, but not in HI. Time to exhaustion in MI₂ tended to improve (393 ± 50 s versus 294 ± 41 s; P = 0.07) in Dex compared with Pla, whereas no difference was detected in HI₂ (106 ± 10 s versus 108 ± 9 s). The results indicate that an increased Na⁺,K⁺ pump expression per se is of importance for thigh K⁺ reuptake at the onset of low and moderate intensity exercise, but less important during high intensity exercise.

(Received 16 August 2007; accepted after revision 26 December 2007; first published online 3 January 2008)
Corresponding author N. Nordsborg: University of Copenhagen, Department of Exercise and Sport Sciences, Section for Human Physiology, Universitetsparken 13, 2100 Copenhagen, Denmark. Email: nnordsborg{at}ifi.ku.dk