Skeletal muscle nNOSμ protein content is increased by exercise training in humans

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McConell, Glenn ORCID: 0000-0002-8572-9065, Bradley, Scott J, Stephens, Terry J, Canny, Benedict J, Kingwell, Bronwyn A and Lee-Young, Robert S (2007) Skeletal muscle nNOSμ protein content is increased by exercise training in humans. American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 293 (2). R821-R828. ISSN 0363-6119


The major isoform of nitric oxide synthase (NOS) in skeletal muscle is the splice variant of neuronal NOS, termed nNOSμ. Exercise training increases nNOSμ protein levels in rat skeletal muscle, but data in humans are conflicting. We performed two studies to determine 1) whether resting nNOSμ protein expression is greater in skeletal muscle of 10 endurance-trained athletes compared with 11 sedentary individuals (study 1) and 2) whether intense short-term (10 days) exercise training increases resting nNOSμ protein (within whole muscle and also within types I, IIa, and IIx fibers) in eight sedentary individuals (study 2). In study 1, nNOSμ protein was ∼60% higher (P < 0.05) in endurance-trained athletes compared with the sedentary participants. In study 2, nNOSμ protein expression was similar in types I, IIa, and IIx fibers before training. Ten days of intense exercise training significantly (P < 0.05) increased nNOSμ protein levels in types I, IIa, and IIx fibers, a finding that was validated by using whole muscle samples. Endothelial NOS and inducible NOS protein were barely detectable in the skeletal muscle samples. In conclusion, nNOSμ protein expression is greater in endurance-trained individuals when compared with sedentary individuals. Ten days of intense exercise is also sufficient to increase nNOSμ expression in untrained individuals, due to uniform increases of nNOSμ within types I, IIa, and IIx fibers.

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Online ISSN: 1522-1490

Item type Article
DOI 10.1152/ajpregu.00796.2006
Official URL
Subjects Historical > FOR Classification > 1101 Medical Biochemistry and Metabolomics
Historical > FOR Classification > 1106 Human Movement and Sports Science
Historical > Faculty/School/Research Centre/Department > Institute of Sport, Exercise and Active Living (ISEAL)
Keywords ResPubID22075. skeletal muscle, nitric oxide synthase protein, exercise, NOS, insulin, diabetes, immunohistochemistry
Citations in Scopus 109 - View on Scopus
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