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This Article Full Text Full Text (PDF) All Versions of this Article: 572/1/281    most recent jphysiol.2005.103366v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Martins, K. J. B. Articles by Putman, C. T. Search for Related Content PubMed PubMed Citation Articles by Martins, K. J. B. Articles by Putman, C. T. Related Collections Skeletal Muscle and Exercise

¹ Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation
² Division of Physical Medicine and Rehabilitation
³ The Centre for Neuroscience, Faculty of Medicine and Dentistry
⁴ Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, AB, Canada T6G 2H9
⁵ Department of Biology, Faculty of Science, University of Konstanz, Konstanz D-78457, Germany

The purpose of this study was to determine whether satellite cell ablation within rat fast-twitch muscles exposed to chronic low-frequency stimulation (CLFS) would limit fast-to-slow fibre-type transitions. Twenty-nine male Wistar rats were randomly assigned to one of three groups. Satellite cells of the left tibialis anterior were ablated by weekly exposure to a 25 Gy dose of -irradiation during 21 days of CLFS (IRR-Stim), whilst a second group received only 21 days of CLFS (Stim). A third group received weekly doses of -irradiation (IRR). Non-irradiated right legs served as internal controls. Continuous infusion of 5-bromo-2'-deoxyuridine (BrdU) revealed that CLFS induced an 8.0-fold increase in satellite cell proliferation over control (mean ±S.E.M.: 23.9 ± 1.7 versus 3.0 ± 0.5 mm^–2, P < 0.0001) that was abolished by -irradiation. M-cadherin and myogenin staining were also elevated 7.7- and 3.8-fold (P < 0.0001), respectively, in Stim compared with control, indicating increases in quiescent and terminally differentiating satellite cells; these increases were abolished by -irradiation. Myonuclear content was elevated 3.3-fold (P < 0.0001) in Stim, but remained unchanged in IRR-Stim. Immunohistochemical analyses revealed attenuation of fast-to-slow fibre-type transitions in IRR-Stim compared with Stim. Comparable changes were observed at the protein level by SDS-PAGE. It is concluded that although considerable adaptive potential exists within myonuclei, satellite cells play a role in facilitating fast-to-slow fibre-type transitions.

(Received 9 December 2005; accepted after revision 19 January 2006; first published online 26 January 2006)
Corresponding author C. T. Putman: E-417 Van Vliet Centre, University of Alberta, Edmonton, Alberta, Canada, T6G 2H9. Email: tputman{at}ualberta.ca

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