Since it is known that the sarcolemmal expression of nNOS is lost in mdx mice [46], and activity [47] and expression level [4] of eNOS is unchanged in the cardiac and skeletal muscles of mdx mice or DMD patients, the high basal level of NO is likely from upregulated expression of inducible NOS (iNOS) [48]. Here, NOS1 is linked to Duchenne muscular dystrophy.