The fibrinolysin system in otitis media with effusion.

Middle ear effusions can cause the fibrinolytic dissolution of human fibrin clots. The data presented herein indicate that the highest level of fibrinolytic activity and general proteolytic activity is found in the serous effusions. The mucoid effusions show the lowest levels of fibrinolytic activity. The significance of the fibrinolytic activity in middle ear fluids is not fully understood. Plasmin, the active protease of the fibrinolysin system, is capable of activating a number of proteolytic systems, including the intrinsic coagulation system, the vasoactive peptide system, and the complement system. All the inflammatory mediator systems can promote increased vascular permeability, tissue edema, and leukocytic migration. The relation of these systems to inflammation in the middle ear may have a profound influence on the possible conversion of a simple middle ear effusion into chronic otitis media.