Effect of dexamethasone on skeletal muscle Na+,K+ pump subunit specific expression and K+ homeostasis during exercise in humans.
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 alpha1 and alpha2 subunit expression was approximately 17% higher (P < 0.05) and the structural beta1 and beta2 subunit expression was approximately 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 (MI(1): 5 min; 2 min recovery; MI(2): exhaustive) and two high-intensity (71.7 +/- 2.5 W) exercise bouts (HI(1): 1 min 40 s; 2 min recovery; HI(2): 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 MI(2) tended to improve (393 +/- 50 s versus 294 +/- 41 s; P = 0.07) in Dex compared with Pla, whereas no difference was detected in HI(2) (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.
Nordsborg
Nikolai
N
University of Copenhagen, Department of Exercise and Sport Sciences, Section for Human Physiology, Universitetsparken 13, 2100 Copenhagen, Denmark. nnordsborg@ifi.ku.dk
Ovesen
Jakob
J
Thomassen
Martin
M
Zangenberg
Mathias
M
Jøns
Christian
C
Iaia
F Marcello
FM
Nielsen
Jens Jung
JJ
Bangsbo
Jens
J
D000328:Adult; D003907:Dexamethasone / Q000494:pharmacology*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000378:metabolism; D008297:Male; D018763:Muscle Fatigue / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology*; D011188:Potassium / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D005938:Glucocorticoids; D007773:Lactates; D021122:Protein Subunits; D003907:Dexamethasone; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium