[The investigation of a low molecular acid stable proteinase inhibitor in the middle ear secretion (author's transl)].

The proteolytic activity of different proteinases during chronic otitis media can be inhibited by alpha-2-macroglobulin and alpha-1-antitrypsin. A new low molecular (13,000) acid stable and polyvalent proteinase inhibitor could be investigated in the middle ear secretion from patients with cholesteatoma and chronic otitis media. We believe that this inhibitor is identical with the low molecular inhibitor of bronchial mucus and the nasal fluid. This inhibitor shows a high anti proteolytic capacity and can inactive trypsin, chymotrypsin, pronase and leucocytic preoteinases. The inhibitor is not detectable in any case. We could find it in 55 cases, three specimens of middle ear secretions obtained no acid stable inhibitor. It is present in the secretion in a masked form by in situ-reaction with leucocytic proteinases. By denaturating deproteinizing it is liberated out of the complex with proteinases and can be measured. The investigations demonstrate that the level of the inhibitor varies during the course of a chronic otitis media. In the postoperative phase the inhibitor concentrations were clearly higher than preoperatively. A steep drop of inhibitor can be observed in cases of chronic otitis with the symptomatology of an acute inflammation. In cases with a chronic inflammation the inhibitor level seems to remain low. The decrease of the inhibitor is explained as a using up effect during reaction between inhibitor and leucocytic proteinases. We believe that this inhibitor in the middle ear secretion results from a limited proteolysis and splitting of inter-alpha-trypsin inhibitor by a proteolytic enzyme, possibly by kallikrein.