Myogenic NOS and endogenous NO production are defective in colon from dystrophic (mdx) mice

The aim of the present study was to evaluate whether alterations in the distribution and/or function of nitric oxide synthase (NOS) could be involved in the development of the spontaneous mechanical tone observed in colon from dystrophic (mdx) mice. By recording the intraluminal pressure of isolated colon from normal mice, we showed that Nω-nitro-L-arginine methyl ester (L-NAME) increased the tone, even in the presence of tetrodotoxin. The effect was prevented by L-arginine, nifedipine, or Ca2+-free solution. In colon from mdx mice, L-NAME was ineffective. Immunohistochemistry revealed that the presence and distribution of neuronal (nNOS), endothelial, and inducible NOS isoforms in smooth m…