Middle ear catalase distribution in an animal model of otitis media.

Increasing evidence implicates free radicals in the pathogenesis of inflammatory disease, including otitis media. The anti-oxidant enzymes catalase, glutathione peroxidase and superoxide dismutase protect tissues from the destructive effects of free radicals. Our previous work has shown depressed levels of superoxide dismutase in the infected middle ears of a guinea pig model of otitis media in comparison with normal control ears. We studied the distribution and relative abundance of catalase in the middle ear of this animal model in an effort to elucidate the role free radicals play in the pathogenesis of otitis media. Catalase distribution was mapped immunohistochemically in the middle ears of guinea pigs with induced streptococcus otitis media, and compared with normal control ears. In the control ears, catalase was localized to the epithelium of the middle ear mucosa, with scant distribution in the submucosa. The infected ears demonstrated inflammatory cell invasion with hyperemia and submucosal edema. Catalase was localized to the epithelium and had scant distribution in the submucosa. This distribution was similar to that found previously with superoxide dismutase. Enzyme-linked immunosorbent assay of catalase demonstrated a mean value of 1.00 +/- 0.06 microgram/mg protein in the control ears, and 1.06 +/- 0.12 microgram/mg in the infected ears, but these two values were not statistically different.