Relationship between functional deficit and severity of experimental fast-strain injury of rat skeletal muscle.
We developed a rat model of fast-strain muscle injury to examine the relationship between functional deficit and the degree of muscle damage. A single fast strain was applied to the right plantaris (Plt) muscle of adult male rats. A tetanic contraction was induced by stimulating the sciatic nerve. Three types of strain injuries were produced by manipulating the timing of strain and contraction conditions, including applying the strain at: (1) the shortening phase (SP), (2) the full contraction phase (FCP) during tetanic contraction and (3) when the muscle is not contracting, i.e. non-contraction (NC). The contralateral Plt muscle was used as the control. Morphological and functional analysis were performed and the severity of strain injury was estimated by measuring [3H]thymidine labelling 48 h after the strain was applied. The results show a significant decrease in tension output in all three groups at 5 min after strain application (P < 0.01). The functional deficit lasted for 3 weeks in the NC group, while rats of the SP and FCP groups showed recovery 1 week after strain. Increased uptake of [3H]thymidine was similar in SP and FCP groups, but 3.5-fold higher in NC than in SP and FCP groups (P < 0.01). Histological analysis revealed an increase in the size of interstitial spaces of the muscle in NC compared to SP and FCP groups (P<0.05). Our results suggest that the contraction of muscle fibres limits the severity of connective tissue damage, and that muscle damage accompanied by disruption of the muscle connective tissue network requires a relatively longer recovery time.
Uchiyama
Y
Y
Department of Orthopaedic Surgery, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, Japan.
Tamaki
T
T
Fukuda
H
H
D000818:Animals; D004195:Disease Models, Animal; D008297:Male; D008938:Mitosis; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000293:injuries* / Q000294:innervation / Q000473:pathology*; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000502:physiology*; D012584:Sciatic Nerve / Q000502:physiology; D013047:Specific Pathogen-Free Organisms; D013180:Sprains and Strains / Q000473:pathology* / Q000503:physiopathology; D013936:Thymidine / Q000493:pharmacokinetics; D014316:Tritium
D014316:Tritium; D013936:Thymidine