Biochemical study of protease inhibitors in normal chinchilla middle ear

Protein concentration and inhibitory capacity of both α1-antitrypsin (α1-AT) and α2-macroglobulin (α2-M) were measured in plasma and middle ear bulla (MEB) washings of chinchillas by use of specific antisera against chinchilla α1-AT and α2-M. Low molecular weight (LMW) trypsin inhibitor also was analyzed in MEB washings. Chinchilla α2-M showed a common antigenicity with human α2-M. The mean value of α1-AT in chinchilla plasma was 412.0 ± 87.8 and that of α2-M was 435.0 ± 117.1 mg/dL. There was a significant relationship between α-AT level and antitryptic activity, and between α2-M level and trypsin binding activity in plasma. The majority of α1-AT and α2-M in plasma is present as free inhibitors unsaturated with proteases. The MEB washings had significant antitryptic activity, which is attributed to both α1-AT and LMW trypsin inhibitors. Inhibitory functions of α1-AT and LMW trypsin inhibitors appear to play an important role in the defense of the normal middle ear mucosa.