Protective role of superoxide dismutase in rat eustachian tubal mucosa against acute otitis media induced by upper respiratory tract infection

Superoxide dismutase has been known to play a role as an anti-oxidative sys tem against oxidative injury during acute inflammation. To investigate the role of superoxide dismutase in eustachian tubal mucosa during acute otitis media (AOM), an animal model was made. Sprague-Dawley rats were inoculated with Streptococcus pneumoniae through the nasal cavity following developme nt of virus-induced upper respiratory infection. The animals were divided i nto three groups according to their tympanic cavity conditions following ba cterial inoculation; inoculated animals with no resultant AOM (no-AOM), ani mals with resultant AOM (AOM) and animals with resolving otitis media (reco very). The changes of superoxide dismutase in each tubal mucosa were compar ed with that of the normal control using immunohistochemistry and immunoblo tting methods. On Western blot, there were little changes of optical densit y and surface area in no-AOM (213.5 +/- 22.4, 13.2 +/- 0.8 mm(2)) and recov ery group (219.3 +/- 18.7, 14.8 +/- 0.7 mm(2)) compared to the normal contr ol (223.5 +/- 26.2, 16.7 +/- 0.4 mm(2)). However, a marked decrease was fou nd in the AOM model (167.6 +/- 19.3, 6.5 +/- 0.9 mm(2)). These findings sug gest that superoxide dismutase may play a role in protecting tubal mucosa f rom free radical injury during AOM.