Protective effect of thrombin inhibition by argatroban in bleomycin-injured PN-1^−/−mice.PN-1^−/− mice were subjected to bleomycin-induced lung injury (BLM; 2 mg/kg) and treated daily with argatroban (9 mg/kg intraperitoneally) . (A) Thrombin activity was measured by a fluorometric method. Data (mean ± SEM; n = 9-11 per group) were analyzed by Kruskall-Wallis test with Dunn’s multiple comparison test. (B) Percentages of surviving PN-1^−/− mice were plotted over a 14-day period. Log-rank test was used to compare the difference between PN-1^−/− mice with BLM and PN-1^−/− mice with BLM plus argatroban (PN-1^−/− BLM: n = 10; PN-1^−/− BLM + argatroban: n = 15; P = .02). The number of platelets (C) and WBCs (D) in BALFs were counted in the hemocytometer. Data (mean ± SEM; n = 6-9 per group) were analyzed by 1-way analysis of variance with Tukey’s multiple comparison test. *P < .05, ***P < .001, ****P < .0001.