Abstract: Objective To study the effects of urokinase on bleomycininduced pulmonary fibrosis in rats and its possible mechanism. Methods 45 male SD rats were randomly divided into three groups: the model group, the control group and the urokinase treatment group. The rats were intratracheally instilled with bleomycin(5mg/kg)or sterile saline. From the second day after bleomycin or sterile saline challenge, by intraperitoneal injection every two days, the urokinase treatment group was given urokinase (27500U/kg), the other two groups were given sterile saline. All the rats were sacrificed on day 28. Histological changes of the lungs were determined by HE staining and Masson′s trichrome staining. The level of transforming growth factor-β1 in BALF was determined by ELISA. Results At day 28, the neutrophil proportion in BALF was 3.1±1.8 in the treatment group, which was significantly lower than that of the model group（9.3±4.1） and higher than that of the control group(2.5±1.3) (P＜0.01)；the score of alveolitis was 0.9±0.7 in the treatment group, which was significantly lower that in the model group (1.7±0.6) (P＜0.01) but was higher than that in the control group(0.2±0.4) (P＜0.05). The pulmonary fibrosis was significantly decreased in the treatment group compared with the model group ［(1.1±0.7) vs (2.0±0.8), P＜0.01). The transforming growth factor-β1 level in BALF in the treatment group also significantly decreased compared with the model group ［(42.5±1.7)ng/ml vs (45.6±0.6), P＜0.01). ConclusionsUrokinase alleviates the bleomycininduced pulmonary fibrosis in rats possibly by inhibiting the expressions of transforming growth factor-β1 in lung.

Key words: Urokinase, Pulmonary fibrosis, Bleomycin, Transforming growth factor-β1