Skeletal muscles of mdx mice were damaged after overload exercise

AIM:To observe the effects of overload exercise on skeletal muscles in X-linked muscular dystrophy(mdx) mice.METHODS:Mdx mice and C57 mice were carried out swimming and hanging tail movement tests (mdx mice as control did not exercise). It lasted for 13 minutes each time per day, and lasted 3 days. Evans blue was injected into tail vain. The mice were killed the next day, and the hind limbs were taken photographs after skins were flayed. The gastrocnemius muscles and diaphragms cryostat sections were made. Under a fluorescence microscope, Evans blue staining was seen. Then the sections were tested by routine HE staining, the histological change of muscles was analyzed under a light microscope.RESULTS:Many blue colored longitudinal lines were observed in skeletal muscles of mdx mice, whereas they were hardly seen in control mdx and C57 mice. Under a fluorescence microscope, some muscle fibers of mdx mice were stained with Evans blue, few muscle fibers of control mdx mice were stained, and C57 mice were not. Under a light microscope, HE staining of muscles showed some degenerated muscle fibers became round in shape and the myonuclei became condensed, or necrotic fibers had amorphous structures, most of them in the degenerated and necrotic fibers of diaphragms C57 mice did not have these changes.CONCLUSION:Overload exercise did harm to skeletal muscles of mdx mice; Vital staining with Evans blue is useful not only for distinguishing degenerating muscle fibers, but also for studying the degeneration process in dystrophin-deficient muscle.