Immunohistochemical Localization of NOS

In the trachea of ferrets and humans, there is colocalization of immunoreactivity for cNOS and VIP (Dey etal., 1993 SpringaU etal., 1994). Although Fischer and co-workers were unable to demonstrate NOS immunoreactivity in the ganglia of the guinea-pig airway 

The role of neuronal NOS in the airways is incompletely understood. The gene encoding the enzymes has been isolated and cloned (Bredt et al., 1991), and a strain of neuronal NOS knockout mice has recently been developed (Huang etal., 1993 O Dell etal., 1994). WhUe these mice had pyloric stenosis (a characteristic that reaffirmed the important role of iNOS in gastrointestinal neurotransmission), they had no obvious abnormalities of airway structure. The relevance of these findings to the human airway remains to be determined, and the data need to be considered in light of the diverse bioactivities of NO in the lung. 

NOS products of neurons, epithelial cells and other cells in the lung have both bronchodilator and inflammatory properties (Gaston etal., 1994b) the specific nature of this bioactivity depends on the chemical characteristics of the functional products in the specific microenvironment under consideration. For example, NO is capable of complexing with and affecting the activity of a variety of metalloproteins and enzymes, such as guanylyl cyclase and ribonucleotide reductase (Nathan, 1992 Stamler et al., 1992). NO can also complex with superoxide anion to form peroxynitrite, which has a cytotoxic immune effector role (Radi etal., 1991 Stamler etal., 1992). Furthermore, NO can form iron nitrosyl complexes, which are the putative intracellular macrophage products of iNOS responsible for lysis of intracellular parasites (Hibbs 

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