Proteolytic activity in burn wound exudates and comparison of fibrin degradation products and protease inhibitors in exudates and sera.
Proteolytic (caseinolytic) activity in burn wound exudates was screened over the range pH 5.3 to 8.4. Although activity was greatest at pH 8.4 in four of seven exudates, individual differences indicated that different proteases predominate in the local environment of the wound. Paired exudate and serum samples were compared with regard to fibrin degradation products and three protease inhibitors: antithrombin III, a1-protease inhibitor, and a2-antiplasmin. Fibrin degradation products concentration was higher in exudates than in paired sera, indicating the wound as the source of circulating fibrin degradation products rather than intravascular coagulation followed by fibrinolysis. In contrast, all three protease inhibitors exhibited higher concentrations in serum than in the paired exudate. The serum/exudate ratio for AT III differed significantly from that for a1-protease inhibitor and a2-antiplasmin, and the ratio of two inhibitors in serum differed from the ratio of the same two inhibitors in the exudate in two of three comparisons. These findings emphasize the importance of exudate examinations as a reflection of events in the wound itself. The importance of microenvironments is invoked to account for the significant exudate fibrin degradation products titers, which are seen despite the presence of antithrombin III, which could inhibit coagulation, and the presence of a2-antiplasmin, which could inhibit fibrin degradation.