ELECTRON-SPIN-RESONANCE SPIN-TRAPPING ASSAY AND IMMUNOHISTOCHEMICAL LOCALIZATION OF SUPEROXIDE DISMUTASES IN THE RAT NASAL-MUCOSA

The immunohistochemical method and electron spin resonance (ESR) spin trapping assay were employed to detect the localization and biochemica l activity of superoxide dismutases (SODs) in the rat nasal mucosa. Ma nganese SOD and copper-zinc SOD were immunohistochemically illustrated to be richly expressed in the epithelial cells and the subepithelial glands of nasal mucosa. The olfactory vesicles also showed positive im munostaining for manganese SOD and copper-zinc SOD. ESR spin trapping assay revealed that SOD activity in the mucosa of olfactory areas was significantly higher than in the mucosa of respiratory areas; however, the ratio of SOD activity in the mitochondrial fraction to SOD activi ty in the cytosolic fraction was similar, approximating 17:83 in the m ucosa of both the olfactory and respiratory areas. The predominant loc alization of SODs in epithelial cells of nasal mucosa suggests the imp ortance of mucosal epithelium in protecting nasal mucosa against cytot oxic superoxide (O2-) radicals. Epithelial goblet cells and the connec tive tissue of lamina propria, which showed no positive immunostaining for SODs, are considered to be vulnerable to oxidative insults implic ated in the generation of O2- radicals. The higher SODs activity in th e mucosa of olfactory areas implies that there is a different requirem ent of SOD in mucosa of the respiratory and olfactory areas on scaveng ing microenvironmental O2- radicals.