Tissue Fibrin Deposition during Acute Lung Injury in Rabbits and Its Relationship to Local Expression of Procoagulant and Fibrinolytic Activities1–3

Abstract
Parenchymal fibrin deposition is well recognized in many forms of acute lung injury. Proteins derived from the actions of the coagulation and fibrinolytic systems may potentiate these inflammatory reactions as well as influence the subsequent repair process. However, the factors regulating fibrin formation and dissolution in acute pneumonitis have not been defined. In this study, we characterized the procoagulant (PC) and fibrinolytic activities simultaneously present in the alveolar space during the course of acute lung injury induced in rabbits by an intravenous injection of phorbol myristate acetate (PMA). Within 6 h of PMA injection, this injury was characterized histologically by extensive intra-alveolar fibrin formation and marked accumulation in pulmonary parenchyma of intravenously administered 125I-fibrinogen. Clearance of fibrin ensued over the remainder of the 72-h study period. Normal BAL fluid contained high levels of procoagulant activity which did not vary after the onset of inflammation. T...