SARCOPLASMIC-ENDOPLASMIC-RETICULUM CA2+-ATPASE AND CALSEQUESTRIN ARE OVEREXPRESSED IN SPARED INTRINSIC LARYNGEAL MUSCLES OF DYSTROPHIN-DEFICIENT MDX MICE

In the mdx mouse model of Duchenne muscular dystrophy, the lack of dystrophin is associated with increased calcium levels and skeletal muscle myonecrosis. The intrinsic laryngeal muscles (ILM) are protected and do not undergo myonecrosis. We investigated whether this protection is related to an increased expression of calcium-binding proteins, which may protect against the elevated calcium levels seen in dystrophic fibers. The expression of sarcoplasmic-endoplasmic-reticulum Ca2+-ATPase and calsequestrin was examined in ILM and in nonspared limb muscles of control and mdx mice using immunofluorescence and immunoblotting. Dystrophic ILM presented a significant increase in the proteins studied when compared to controls. The increase of Ca2+-handling proteins in dystrophic ILM may permit better maintenance of calcium homeostasis, with the consequent absence of myonecrosis. The results further support the concept that abnormal Ca2+-handling is involved in dystrophinopathies.