Expression of
aquaporin (AQP) 4 in the surface membranes of skeletal myofibers is well established; however, its functional significance is still unknown. The alterations of AQP4 expressions in dystrophic muscles at
RNA and
protein levels have been reported in various dystrophic muscles such as dystrophinopathy,
dysferlinopathy, and
sarcoglycanopathy. We are interested in the relationship between the severity of dystrophic muscle degeneration and the expression of AQP4. Here we compared the AQP4 expression of the limb muscles with that of diaphragms in both mdx and control mice. The dystrophic muscle degeneration, such as rounding profile of cross sectional myofiber shape, dense
eosin staining, central nuclei, and endomysial
fibrosis in mdx mice, were more marked in diaphragms than in limb muscles. The decrease of AQP4 expression at
protein level was more marked in diaphragms than in the limb muscles of mdx mice. However, the expression of AQP4
mRNA in the diaphragms of mdx mice was not reduced in comparison with limb muscles of mdx mice. The present study revealed that AQP4 expression at
protein level was correlated with the severity of dystrophic changes in muscle tissues of mdx mice.