Objective: To study the production of nitric oxide (NO), and the presence of different isoforms of the NO-synthesising enzyme, NO-synthase (NOS), in the paranasal sinus.
Materials and methods: Ten patients, undergoing surgery for pituitary adenoma, were examined for the presence of NO gas in the sphenoidal and maxillary sinus. The distribution of different NOS isozymes in mucosal biopsies from sphenoid and maxillary sinus and ethmoidal cells was studied.
Results: The mean concentration of NO was 2575 ppb in the sphenoidal sinus and 6792 ppb in the maxillary sinus. Morphological analyses revealed intense NADPH-diaphorase staining throughout the epithelium. Immunoreactivity against NOS2 (inducible NOS) was observed in the apical cell layer but not of the basal layer. NOS1 (neuronal NOS)-immunoreactivity was mainly seen in the subapical part of the epithelium and NOS3 (endothelial NOS)-immunoreactivity was observed only in the most apical part of the epithelium.
Conclusion: NO concentration in the sphenoidal sinus is about the same as in the nasal cavity and approximately half of the concentration found in the maxillary sinus. All of the three main different isozymes of NOS can be demonstrated in the mucosa of the sphenoidal and maxillary sinus and ethmoidal cells, NOS2 being the most abundant isoform.