Intense exercise up-regulates Na+,K+-ATPase isoform mRNA, but not protein expression in human skeletal muscle.
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 approximately 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 alpha(1), alpha(2), alpha(3), beta(1), beta(2) and beta(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 alpha(3) and beta(2) mRNA by 2.4- and 1.7-fold, respectively (P < 0.05), whilst alpha(1) and alpha(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 beta(1) and beta(3) mRNA, reflecting variable time-dependent responses. When the average postexercise value was contrasted to rest, mRNA increased for alpha(1), alpha(2), alpha(3), beta(1), beta(2) and beta(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 alpha(1)-alpha(3) and beta(1)-beta(3) isoforms. Thus, human skeletal muscle expresses each of the Na(+),K(+)-ATPase alpha(1), alpha(2), alpha(3), beta(1), beta(2) and beta(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.
Murphy
K T
KT
School of Human Movement, Recreation and Performance (FO22), Victoria University of Technology, PO Box 14428, MCMC, Melbourne, Victoria, Australia.
Snow
R J
RJ
Petersen
A C
AC
Murphy
R M
RM
Mollica
J
J
Lee
J S
JS
Garnham
A P
AP
Aughey
R J
RJ
Leppik
J A
JA
Medved
I
I
Cameron-Smith
D
D
McKenna
M J
MJ
D000328:Adult; D002478:Cells, Cultured; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000201:enzymology; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology
D007527:Isoenzymes; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase