Lack of coordinated changes in metabolic enzymes and myosin heavy chain isoforms in regenerated muscles of trained rats.
We investigated training-induced changes in biochemical properties and myosin heavy chain (MHC) composition of regenerated (cardiotoxin-injected) plantaris muscles (PLA) in rats either maintained sedentary (S, n = 9) or endurance trained on a treadmill over a 8-week period (T, n = 7). Both endurance training and regeneration altered the pattern of fast MHC expression. An analysis of the two-way interaction between training and regeneration showed that the relative content of type IIa MHC was affected (P < 0.05). The 140% increase in type IIa MHC observed in regenerated PLA from T rats compared with nontreated muscle of S rats, exceeded the 102% increase resulting from the combination of regeneration alone (26%) and training alone (61%). A similar interaction between training and regeneration was shown for the percentage of fibres expressing either type IIa or type lIb MHC (P < 0.05). In contrast, a significant increase in the citrate synthase (CS) activity was shown in PLA as a result of endurance training, without specific effect of regeneration. Furthermore, training-induced changes in CK and LDH isoenzyme distribution occurred to a similar extent in regenerated and non-treated PLA muscles, and thus did not follow the changes in MHC isoforms. An increase in the mitochondrial CK isozyme activity (mi-CK) was shown in both non-treated and previously degenerated PLA muscles (123 and 117%, P < 0.01, respectively), without specific effect of regeneration. The ratio of mi-CK to CS activity, an estimate of the mitochondrial specific activity of mi-CK was significantly increased by training (P < 0.02) and decreased by regeneration (P < 0.05). Taken together, these data suggest that while training and regeneration have cumulative effects on the pattern of fast MHC expression, the training-induced changes in the energy metabolism shown in mature non-treated myofibres are similar to those observed in regenerated fibres.
Bigard
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AX
Unité de Bioénergétique et Environnement, Centre de Recherches du Service de Santé des Armées, La Tronche, France. BIGARDXavier@compuserve.com
Mateo
P
P
Sanchez
H
H
Serrurier
B
B
Ventura-Clapier
R
R
D000818:Animals; D002950:Citrate (si)-Synthase / Q000502:physiology; D004179:Cobra Cardiotoxin Proteins / Q000633:toxicity; D005260:Female; D007527:Isoenzymes / Q000502:physiology; D007770:L-Lactate Dehydrogenase / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology; D020033:Protein Isoforms / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000502:physiology
D004179:Cobra Cardiotoxin Proteins; D007527:Isoenzymes; D020033:Protein Isoforms; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains