Protease inhibitors in middle ear effusions from experimental otitis media with effusion: kinetics of alpha 1-antitrypsin and alpha 2-macroglobulin levels.

Alpha 1-antitrypsin (alpha 1-AT) and alpha 2-macroglobulin (alpha 2-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 alpha 1-AT in SOM was significantly higher than that in POM (p less than .01) because of the high alpha 1-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 less than .01, less than .05), and significantly lower than that in SOM (p less than .01). The majority of both inhibitors in SOM exists 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 alpha 1-AT and alpha 2-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.