title: "Fast" and "slow" muscle fibres in hindlimb muscles of adult rats regenerate from intrinsically different satellite cells.
abstract: Myosin heavy chain (MyHC) expression was examined in regenerating fast extensor digitorum longus (EDL) and slow soleus (SOL) muscles of adult rats. Myotoxic bupivacaine was injected into SOL and EDL and the muscles were either denervated or neuromuscularly blocked by tetrodotoxin (TTX) on the sciatic nerve. Three to 10 or 30 days later, denervated SOL or EDL, or innervated but neuromuscularly blocked EDL received a slow 20 Hz stimulus pattern through electrodes implanted on the muscles or along the fibular nerve to EDL below the TTX block. In addition, denervated SOL and EDL received a fast 100 Hz stimulus pattern. Denervated EDL and SOL stimulated with the same slow stimulus pattern expressed different amounts of type 1 MyHC protein (8% versus 35% at 10 days, 13% versus 87% at 30 days). Stimulated denervated and stimulated innervated (TTX blocked) EDL expressed the same amounts of type 1, 2A, 2X and 2B MyHC proteins. Cross-sections treated for in situ hybridization and immunocytochemistry showed expression of type 1 MyHC in all SOL fibres but only in some scattered single or smaller groups of fibres in EDL. The results suggest that muscle fibres regenerate from intrinsically different satellite cells in EDL and SOL and within EDL. However, induction by different extrinsic factors arising in extracellular matrix or from muscle position and usage in the limb has not been excluded. No evidence for nerve-derived trophic influences was obtained.
authors.affiliation: Department of Physiology, PO Box 1103, Blindern, 0317 Oslo, Norway. j.m.kalhovde@basalmed.uio.no
authors.forename: J M
authors.initials: JM
authors.lastname: Kalhovde
authors.forename: R
authors.initials: R
authors.lastname: Jerkovic
authors.forename: I
authors.initials: I
authors.lastname: Sefland
authors.forename: C
authors.initials: C
authors.lastname: Cordonnier
authors.forename: E
authors.initials: E
authors.lastname: Calabria
authors.forename: S
authors.initials: S
authors.lastname: Schiaffino
authors.forename: T
authors.initials: T
authors.lastname: Lømo
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D004558:Electric Stimulation; D005786:Gene Expression Regulation / Q000502:physiology; D006614:Hindlimb / Q000502:physiology; D008297:Male; D009121:Muscle Denervation; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000294:innervation / Q000502:physiology* / Q000601:surgery; D018995:Myosin Heavy Chains / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000502:physiology*; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000502:physiology*
chemical_list: D009124:Muscle Proteins; D018995:Myosin Heavy Chains