Intense exercise up-regulates Na+,K+-ATPase isoform mRNA, but not protein expression in human skeletal muscle

• Published in: The Journal of physiology Vol. 556; no. 2; pp. 507 - 519
• Main Authors: Murphy, K. T., Snow, R. J., Petersen, A. C., Murphy, R. M., Mollica, J., Lee, J. S., Garnham, A. P., Aughey, R. J., Leppik, J. A., Medved, I., Cameron‐Smith, D., McKenna, M. J.
• Format: Journal Article
• Language: English
• Published: 9600 Garsington Road , Oxford , OX4 2DQ , UK The Physiological Society 15.04.2004; Blackwell Science Ltd; Blackwell Science Inc
• Subjects: Adult; Cells, Cultured; Exercise - physiology; Female; Humans; Isoenzymes - genetics; Male; Muscle Fibers, Skeletal - cytology; Muscle Fibers, Skeletal - enzymology; Muscle, Skeletal - cytology; Muscle, Skeletal - physiology; Research Papers; RNA, Messenger - metabolism; Sodium-Potassium-Exchanging ATPase - genetics; Sodium-Potassium-Exchanging ATPase - metabolism; Up-Regulation - physiology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2003.054981

Characterization of expression of, and consequently also the acute exercise effects on, Na + ,K + -ATPase isoforms in human skeletal muscle remains incomplete and was therefore investigated. Fifteen healthy subjects (eight males, seven females) performed fatiguing, knee extensor exercise at ∼40% of their maximal work output per contraction. A vastus lateralis muscle biopsy was taken at rest, fatigue and 3 and 24 h postexercise, and analysed for Na + ,K + -ATPase α 1 , α 2 , α 3 , β 1 , β 2 and β 3 mRNA and crude homogenate protein expression, using Real-Time RT-PCR and immunoblotting, respectively. Each individual expressed gene transcripts and protein bands for each Na + ,K + -ATPase isoform. Each isoform was also expressed in a primary human skeletal muscle cell culture. Intense exercise (352 ± 69 s; mean ± s.e.m. ) immediately increased α 3 and β 2 mRNA by 2.4- and 1.7-fold, respectively ( P < 0.05), whilst α 1 and α 2 mRNA were increased by 2.5- and 3.5-fold at 24 h and 3 h postexercise, respectively ( P < 0.05). No significant change occurred for β 1 and β 3 mRNA, reflecting variable time-dependent responses. When the average postexercise value was contrasted to rest, mRNA increased for α 1 , α 2 , α 3 , β 1 , β 2 and β 3 isoforms, by 1.4-, 2.2-, 1.4-, 1.1-, 1.0- and 1.0-fold, respectively ( P < 0.05). However, exercise did not alter the protein abundance of the α 1 –α 3 and β 1 –β 3 isoforms. Thus, human skeletal muscle expresses each of the Na + ,K + -ATPase α 1 , α 2 , α 3 , β 1 , β 2 and β 3 isoforms, evidenced at both transcription and protein levels. Whilst brief exercise increased Na + ,K + -ATPase isoform mRNA expression, there was no effect on isoform protein expression, suggesting that the exercise challenge was insufficient for muscle Na + ,K + -ATPase up-regulation.