Contraction-induced changes in skeletal muscle Na+,K+ pump mRNA expression – importance of exercise intensity and Ca2+-mediated signalling
To investigate if exercise intensity and Ca2+ 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 Ca2+ 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 ∼85% of VO2peak increased (P < 0.05) α1 and β1 mRNA expression ∼2-fold in untrained and trained subjects. In trained subjects, intermittent exercise at ∼70% of VO2peak resulted in a less (P < 0.05) pronounced increase (∼1.4-fold; P < 0.05) for α1 and no change in β1 mRNA. Prolonged low intensity exercise increased (P < 0.05) mRNA expression of α1 ∼3.0-fold and α2 ∼1.8-fold in untrained but not in trained subjects. Electrical stimulation of rat soleus, but not EDL, muscle increased (P < 0.05) α1 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) α1 and reduced (P < 0.001) α2 mRNA expression and these responses were abolished (P < 0.05) by co-incubation with cyclosporin A or KN62. Conclusion:
(1) Exercise-induced increases in Na+,K+ pump α1 and β1 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 α1 mRNA expression in untrained subjects. (3) Ca2+i regulates α1 mRNA expression in oxidative muscles via Ca2+/calmodulin-dependent protein kinase (CaMK) and calcineurin signalling pathways.
Document Type: Research Article
Affiliations: 1: Department of Exercise and Sport Sciences, Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark 2: Department of Biology, Copenhagen Muscle Research Centre and Centre of Inflammation and Metabolism, University of Copenhagen, Copenhagen Ø, Denmark 3: Department of Sport Science, University of Aarhus, Aarhus, Denmark
Publication date: 2010-04-01