Biochemical study of protease inhibitors in normal chinchilla middle ear.

Protein concentration and inhibitory capacity of both alpha 1-antitrypsin (alpha 1-AT) and alpha 2-macroglobulin (alpha 2-M) were measured in plasma and middle ear bulla (MEB) washings of chinchillas by use of specific antisera against chinchilla alpha 1-AT and alpha 2-M. Low molecular weight (LMW) trypsin inhibitor also was analyzed in MEB washings. Chinchilla alpha 2-M showed a common antigenicity with human alpha 2-M. The mean value of alpha 1-AT in chinchilla plasma was 412.0 +/- 87.8 and that of alpha 2-M was 435.0 +/- 117.1 mg/dL. There was a significant relationship between alpha 1-AT level and antitryptic activity, and between alpha 2-M level and trypsin binding activity in plasma. The majority of alpha 1-AT and alpha 2-M in plasma is present as free inhibitors unsaturated with proteases. The MEB washings had significant antitryptic activity, which is attributed to both alpha 1-AT and LMW trypsin inhibitors. Inhibitory functions of alpha 1-AT and LMW trypsin inhibitors appear to play an important role in the defense of the normal middle ear mucosa.