IMMUNOHISTOCHEMICAL LOCALIZATION OF NITRIC-OXIDE SYNTHASE ACTIVITY INUPPER RESPIRATORY EPITHELIUM

Nitric oxide (NO) production in the respiratory epithelium of the uppe r airways has recently been described. To better delineate the role of epithelial NO, the authors of this study attempted to identify the ce ll type responsible for the production of NO in rat tracheal epitheliu m and human nasal epithelium. They localized the activity of NO throug h immunohistochemical analysis with an antibody to L-citrulline, a mar ker for activity of the L-arginine-dependent nitric oxide synthase (NO S) pathway. Using anti-inducible NOS (iNOS) and anti-constitutive NOS (cNOS) antibodies, they also attempted to identify the specific NO iso types that were present. The tracheal and nasal epithelium demonstrate d strong immunoreactivity to citrulline in ciliated cells. The ciliate d cells of the nasal turbinates demonstrated strong iNOS positivity, b ut no significant cNOS immunoreactivity, The study findings that iNOS activity is present in ciliated epithelial cells of rat and human uppe r respiratory epithelium suggest that NO may play a role in epithelial homeostasis and could potentially play a role in the pathogenesis of mucociliary dysfunction.