Posttetanic potentiation in mdx muscle

作者：Smith Ian Curtis; Huang Jian; Quadrilatero Joe; Tupling Allan Russell; Vandenboom Rene^*

来源：Journal of Muscle Research and Cell Motility, 2010, 31(4): 267-277.

DOI：10.1007/s10974-010-9229-2

• Muscular dystrophy
• Myosin regulatory light chain
• Myosin heavy chain
• Fiber type
• Extensor digitorum longus
• Skeletal muscle

X-linked muscular dystrophy of the mouse (mdx) has been reported to progressively remodel skeletal muscle to preferentially reduce fast fiber composition. Despite this, mdx muscle displays normal levels of posttetanic potentiation (PTP). Since PTP may primarily depend on phosphorylation of the myosin regulatory light chain (RLC) in fast muscle fibers, maintenance of PTP with mdx disease progression is paradoxical and may represent an adaptation of the diseased muscle. This study assesses the role of RLC phosphorylation during PTP of mdx muscle. Extensor digitorum longus muscles were isolated from mdx and from C57BL/10 (control) mice at similar to 50 (young) and similar to 300 (adult) days and stimulated in vitro (25A degrees C) to induce PTP. During potentiation, muscles were harvested for subsequent determination of RLC phosphorylation levels. Immunofluorescence was used to assess muscle fiber type composition and no age effects were found. The magnitude of PTP was higher (P < 0.05) in mdx than control muscles at both young (mdx: 21.9 +/- A 1.6%; control: 17.7 +/- A 1.2%) and adult (mdx: 30.4 +/- A 1.8%; control: 23.2 +/- A 2.2%) ages. However, RLC phosphate content was similar between all groups both at rest and following stimulation. Our results are consistent with a model where the sensitivity of mdx muscle to RLC phosphorylation-induced force potentiation is increased by disease- and age-dependent alterations in excitation-contraction coupling noted for mdx and aging muscle.

• 出版日期2010-12