The Change Of Coagulation And Fibrinolysis Activity In Bleomycin-induced Lung Fibrosis In Rat

Idiopathic pulmonary fibrosis is an interstitial lung disease, characterized by hynoxia and dyspnoea and a poor prognosis. Understanding of the pathogenesis of this disorder remains unclear. Apart from inflammatory reaction caused by cytokine, recent investigation have established that coagulation and fibrinolysis system appeared to contribute to the pathogenesis of fibrotic response. Because of procoagulation substance, the procoagulation activity is increased and the coagulation system is abnormal. plasminogen activity inhibitor-1 (PAI-1) ,a major inhibitor of fibrinolysis system , has been implicated in disordered alveolar fibrin clearance and subsequent pulmonary fibrosis.Objective: To study the responses of procoagulation activity (PCA) and PAI-1 activity in bronchoalveolar lavage fluid (BALF) and the expression of PAI-1 in the Bleomycin (BLM)-induced lung injury in rat, and further investigate the change law of coagulation and fibrinolysis system in lung fibrosis and how they play their roles in the pathogenesis of lung fibrosis. Methods: 48 Sprague-Dawley male rats weighing 180g—250g were randomly divided into control group and BLM group,(n=24 animals/group). After anesthesia by Ketamine(100mg/kg),open nuchae, expose bronchi. Lung fibrosis was induced by intratracheal injection BLMA5 (5㎎/㎏) (0.2—0.3ml) and control animals were treated with intratracheal stgerila saline vehicle. Rats were killed randomly at 7day, 14day, 28day and 40day(each group n=6 at each point). Left lung was lavaged by 4℃saline, after which the BALF was centrifuged and stored at ﹣70 degrees. To determine recalcification time for studying PCA and activity of PAI-1 for studying fibrinolysis activity in the lavage fluid. A 2% homogenate of lung tissue from the right first to be stored in﹣70 degrees was used to determine the level of Hydroxyproline(HYP). Other right lung tissues were preserved in 10% formalin for histologic interpretation. HE staining was used to investigate alveolitis. Masson staining was used to investigate the extent of collagen deposition.To be classified by the method of Szapiel for studying the development alveolitis and lung fibrosis. Immunohistochemistry was used to evaluate PAI-1 expression in the lung tissue and to calculate positive index for investigation the development of PAI-1 expression. In order to study the relation about expression of PAI-1 and severity of pulmonary fibrosis, PAI-1 expression and the level of Hydroxyproline were correlated. The date were analyzed using the SAS system .Results: (1) The level of hydroxyproline in control group was not upregulated (p＝0.7538). At 7 day in BLM group, it was 1.13±0.18μg /mg, but did not differ from control values(p﹥0.01). From 14 day to 40 day , it progressively upregulated in BLM versus control group ( p﹤0.01). (2) The BALF recalcification time did not differ in control group(p﹥0.01).In BLM group, the recalcification time of normal pooled plasma in BALF was the shortest in 7 day after induction of lung injury(mean±Dev, 55.62±9.73 sec), the difference was significant versus control group at that interval ( p﹤0.01). In 14 day, the recalcification time was longer than 7 day and the difference was significant (p﹤0.01) versus control group , in 28 and 40 day, the mean recalcification time were 172.46±11.38 sec and 179.55±6.06 sec respectively ,the differences were no significant(p﹥0.01). (3) PAI-1 activity was upregulated continuously from 7 day to 40 day in BLM group, the differences were significant (p﹤0.01),while level in control BALF did not change(p＝0.6817).(4) The result of immunohistochemistry showed that there was no detectable expression of PAI-1 in control group. In BLM group, PAI-1 was expressed in macrophages and II type epithelial cell . At 7day, PAI-1 was expressed weakly, but the expression index was increased during the transition from alveolitis to lung fibrosis. The positive index at 7day and 14 day indicated that PAI-1 expression was increased versus at 40 day and the dif...