Abstract: Objective To investigate the protective effect and its possible mechanism of ulinastatin on lung injury caused by hip fracture. MethodsTotal 24 SD rats were randomly divided into control, hip fracture and hip fracture+ulinastatin groups (n=8). The rats of hip fracture and hip fracture+ulinastatin groups made the left hip fracture. The tail vein of rats of hip fracture+ulinastatin group were injected with 50 000 U/kg ustodin before made fracture model. Killed rats 24 h after mold building. Serum mtDNA, tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in bronchoalveolar lavage fluid, Toll like receptor-9 (TLR9) and nuclear factor (NF)-κB protein expression in lung tissue, wet/dry ratio and pathological scores of lung were detected in all three groups. ResultsSerum mtDNA, TNF-α and IL-6 in bronchoalveolar lavage fluid, TLR9 and NF-κB protein expressions in lung tissue, wet/dry ratio and pathological scores of lung in hip fracture group were significantly higher than those in control group ( P<0.05). Ulinastatin significantly reduced the levels of serum mtDNA, TNF-α and IL-6 in bronchoalveolar lavage fluid, TLR9 and NF-κB protein expressions in lung tissue, as well as wet/dry ratio and pathological scores of lung ( P<0.05). ConclusionUlinastatin might could provide protection on lung injury in hip fracture, and mtDNA-TLR9-NF-κB pathway may play the role of reducing inflammatory level in the process.