Protease inhibitors in middle ear effusions from experimental otitis media with effusion: Kinetics of α1-antitrypsin and α2-macroglobulin levels

Alpha 1-antitrypsin (α1-AT) and alpha 2-macroglobulin (α2-M) were measured by both immunochemical and functional assays in paired plasma and middle ear effusions (MEEs) from experimental otitis media models (serous otitis media [SOM], purulent otitis media [POM], and SOM + POM). The MEE/plasma ratio of α1-AT in SOM was significantly higher than that in POM (p<.01) because of the high α1-AT level in POM plasma. The ratio of both antitryptic activity and trypsin-binding activity in POM was significantly higher than that in SOM + POM (p<.01, <.05), and significantly lower than that in SOM (p<.01). The majority of both inhibitors in SOM exist as the free state, and the reaction between proteases and inhibitors in POM and SOM + POM is more active than that in SOM. It is concluded that both α1-AT and α2-M appear to play an important role in the protection of middle ear mucosa by forming protease-inhibitor complexes to reduce proteolytic damage in POM and SOM + POM models.