Objective: There is functional and morphological evidence that interstitial cells of Cajal (ICC) may play a role in nitric oxide (NO) dependent signal transduction. However, little is known about the nitric oxide synthase (NOS) containing ICC during inflammation. Materials and Methods: Immunocytochemical methods were used for the ultrastructural localization of NOS1-containing ICC in the wall of the colon of rats in experimental colitis. Results: Large numbers of NOS immunoreactive (IR) nerve terminals were found in very close vicinity to smooth muscle cells as well as to blood vessels. IR nerves were found in close relationship with the ICC. The gap between the NOS IR nerve fibers and the membrane of smooth muscle cells and of ICC was 20-250 nm. In experimental colitis the number of NOS IR nerve fibers slightly decreased, however, large numbers (24%) of the ICC became IR for NOS. In the non-inflamed area and in the controls, all these cells were immunonegative for NOS. Conclusions: Our light- and ultrastructural study suggests that some of the ICC can also synthesize NO, at least during inflammation. Therefore the change in the number and structure of ICC could play an important role in the pathogenesis of a variety of motility disorders.
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