title: Effect of satellite cell ablation on low-frequency-stimulated fast-to-slow fibre-type transitions in rat skeletal muscle.
abstract: 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 gamma-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 gamma-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 gamma-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 gamma-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.
authors.affiliation: E-417 Van Vliet Centre, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Karen J B
authors.initials: KJ
authors.lastname: Martins
authors.forename: Tessa
authors.initials: T
authors.lastname: Gordon
authors.forename: Dirk
authors.initials: D
authors.lastname: Pette
authors.forename: Walter T
authors.initials: WT
authors.lastname: Dixon
authors.forename: George R
authors.initials: GR
authors.lastname: Foxcroft
authors.forename: Ian M
authors.initials: IM
authors.lastname: Maclean
authors.forename: Charles T
authors.initials: CT
authors.lastname: Putman
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004558:Electric Stimulation; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology* / Q000648:ultrastructure*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology* / Q000648:ultrastructure*; D018482:Muscle, Skeletal / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D032496:Satellite Cells, Skeletal Muscle / Q000502:physiology* / Q000648:ultrastructure*