Contraction-induced changes in skeletal muscle Na(+), K(+) pump mRNA expression - importance of exercise intensity and Ca(2+)-mediated signalling.
OBJECTIVE
To investigate if exercise intensity and Ca(2+) signalling regulate Na(+),K(+) pump mRNA expression in skeletal muscle.


METHODS
The importance of exercise intensity was evaluated by having trained and untrained humans perform intense intermittent and prolonged exercise. The importance of Ca(2+) signalling was investigated by electrical stimulation of rat soleus and extensor digitorum longus (EDL) muscles in combination with studies of cell cultures.


RESULTS
Intermittent cycling exercise at approximately 85% of VO(2peak) increased (P < 0.05) alpha1 and beta1 mRNA expression approximately 2-fold in untrained and trained subjects. In trained subjects, intermittent exercise at approximately 70% of VO(2peak) resulted in a less (P < 0.05) pronounced increase ( approximately 1.4-fold; P < 0.05) for alpha1 and no change in beta1 mRNA. Prolonged low intensity exercise increased (P < 0.05) mRNA expression of alpha1 approximately 3.0-fold and alpha2 approximately 1.8-fold in untrained but not in trained subjects. Electrical stimulation of rat soleus, but not EDL, muscle increased (P < 0.05) alpha1 mRNA expression, but not when combined with KN62 and cyclosporin A incubation. Ionomycin incubation of cultured primary rat skeletal muscle cells increased (P < 0.05) alpha1 and reduced (P < 0.001) alpha2 mRNA expression and these responses were abolished (P < 0.05) by co-incubation with cyclosporin A or KN62.


CONCLUSIONS
(1) Exercise-induced increases in Na(+),K(+) pump alpha1 and beta1 mRNA expression in trained subjects are more pronounced after high- than after moderate- and low-intensity exercise. (2) Both prolonged low and short-duration high-intensity exercise increase alpha1 mRNA expression in untrained subjects. (3) Ca(2+)(i) regulates alpha1 mRNA expression in oxidative muscles via Ca(2+)/calmodulin-dependent protein kinase (CaMK) and calcineurin signalling pathways.
Nordsborg
N B
NB
Department of Exercise and Sport Sciences, Copenhagen Muscle Research Centre, University of Copenhagen, Denmark. nnordsborg@ifi.ku.dk <nnordsborg@ifi.ku.dk>
Kusuhara
K
K
Hellsten
Y
Y
Lyngby
S
S
Lundby
C
C
Madsen
K
K
Pilegaard
H
H
D000328:Adult; D000818:Animals; D015444:Exercise / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase