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Contraction‐induced changes in skeletal muscle Na + ,K + pump mRNA expression – importance of exercise intensity and Ca 2+ ‐mediated signalling
Author(s) -
Nordsborg N. B.,
Kusuhara K.,
Hellsten Y.,
Lyngby S.,
Lundby C.,
Madsen K.,
Pilegaard H.
Publication year - 2010
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2009.02057.x
Subject(s) - medicine , endocrinology , skeletal muscle , stimulation , messenger rna , ionomycin , gene expression , incubation , chemistry , biochemistry , gene
Aim: 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 ∼85% of V O 2peak increased ( P < 0.05) α1 and β1 mRNA expression ∼2‐fold in untrained and trained subjects. In trained subjects, intermittent exercise at ∼70% of V O 2peak 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) Ca 2+ i regulates α1 mRNA expression in oxidative muscles via Ca 2+ /calmodulin‐dependent protein kinase (CaMK) and calcineurin signalling pathways.