title: Susceptibility to sarcomere injury induced by single stretches of maximally activated muscles of mdx mice.
abstract: The purpose was to investigate the contribution of mechanical damage to sarcomeres to the greater susceptibility of dystrophic muscle fibers to contraction-induced injury. Single stretches provide an effective method for studying mechanical factors that contribute to the initiation of contraction-induced injury. We hypothesized that, after single stretches, the deficits in isometric force would be greater for muscles of mdx than C57BL/10 mice, whereas membrane damage would be minimal for all muscles. Extensor digitorum longus (EDL) and soleus muscles of mice were removed under anesthesia with Avertin (tribromoethanol). During the plateau of a maximum isometric contraction in vitro, muscles were stretched through single strains of 20-60% fiber length. Isometric force was remeasured 1 min later, and muscles were then incubated in procion orange dye to identify fibers with membrane damage. Force deficits at 1 min were two- to threefold greater for EDL muscles of mdx compared with C57BL/10 mice, whereas no significant differences were observed between soleus muscles of mdx and C57BL/10 mice. For all muscles, membrane damage was minimal and not significantly increased by single stretches for either strain of mice. These data support a critical role of dystrophin maintaining sarcomere stability in EDL muscles, whereas soleus muscles retain abilities, in the absence of dystrophin, not different from control muscles to resist sarcomere damage.
authors.affiliation: Institute of Gerontology, University of Michigan, Ann Arbor, Michigan 48109-2007, USA.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Consolino
authors.forename: Susan V
authors.initials: SV
authors.lastname: Brooks
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000293:injuries* / Q000503:physiopathology*; D009137:Muscular Dystrophy, Animal / Q000503:physiopathology*; D012518:Sarcomeres / Q000502:physiology*; D013180:Sprains and Strains / Q000503:physiopathology*