A protease-antiprotease system in antrochoanal polyp. I. Evidence for the existence of proactivator

Tissue extract of antrochoanal polyps showed a faint lysis area on standard fibrin plates, but streptokinase (SK)-added tissue extract showed a large lysis area. No fibrinolytic activity was observed on plasminogen-free fibrin plates. It is concluded, therefore, that the fibrinolytic activity observed after SK addition is indicative of the existence of SK-responsive protein proactivator. The tissue extract did not contain plasminogen or antiprotease against trypsin or papain. It was stable at neutral pH at 37 degrees C and stable at acid pH at 70 degrees C. The role of proactivator is discussed in relation to the growth or enlargement of antrochoanal polyps.