Author/Editor     Pette, Dirk; Sketelj, Janez; Škorjanc, Dejan; Leisner, Elmi; Traub, Irmtrud; Bajrović, Fajko
Title     Partial fast-to-slow conversion of regenerating rat fast-twich muscle bz chronic low-frequency stimulation
Type     članek
Source     J Muscle Res Cell Motil
Vol. and No.     Letnik 23
Publication year     2002
Volume     str. 215-21
Language     eng
Abstract     Chronic low-frequency stimulation (CLFS) of rat fast-twitch muscles induces sequential transitions in myosin heavy chain (MHC) expression from MHCIIb 'MHCIId/x' MHCIIa. However, the 'final' step of the fast-to-slow transition, i.e., the upregulation of MHCI, has been observed only after extremely long stimulation periods. Assuming that fibre degeneration/regeneration might be involved in the upregulation of slow myosin, we investigated the effects of CLFS on extensor digitorum longus (EDL) muscles regenerating after bupivacaine-induced fibre necrosis. Normal, non-regenerating muscles responded to both 30- and 60-day CLFS with fast MHC isoform transitions (MHCIIb -` MHCIId ` MHCIIa) and only slight increases in MHCI. CLFS of regenerating EDL muscles caused similar transitions among the fast isoforms but, in addition, caused significant increases in MHCI (to `30% relative concentration). Stimulation periods of 30 and 60 days induced similar changes in the regenerating bupivacaine-treated muscles, indicating that the upregulation of slow myosin was restricted to regenerating fibres, but only during an early stage of regeneration. These results suggest that satellite cells and/or regenerating fast rat muscle fibres are capable of switching directly to a slow program under the influence of CLFS and, therefore, appear to be more malleable than adult fibres.
Descriptors     MUSCLE, SKELETAL
MUSCLE FIBERS, FAST-TWITCH
MYOSIN HEAVY CHAINS
BUPIVACAINE
ELECTRIC STIMULATION
ELECTROPHORESIS
DENSITOMETRY
MUSCLE FIBERS, SLOW-TWITCH
RATS