Objective To investigate the effects of inhaled prostaglandin E1 (PGE1)on Th1/Th2 polarity in rat model of lipopolysaccharide(LPS) induced acute lung injury(ALI).Methods Healthy adult male Wistar rats [weight (200±20)g] were randomly divided into normal control(NS) group,LPS group and PGE1 group.The model of ALI were established by injecting LPS of 5 mg/kg into caudal vein.The rats in PGE1 group inhaled aerosolized PGE1(2 μg/mL)for 30 minutes after LPS injection,then repeat the procedure 12 hours later. 1 h,6 h,12 h and 24 h after last PGE1 inhalation,enzyme linked immunosorbant assay (ELISA) was empolyed to measure the level of interferon-γ(IFN-γ)and interleukin-4(IL-4)in the serum and bronchoalveolar lavage fluid(BALF)and the ratio of IFN-γ/IL-4(Th1/Th2)was calculated.Pathological examination was made under light microscope.Results Pathological examination of lung tissue demonstrated success ALI model.Compared to NS group,the ratio of IFN-γ/IL-4(Th1/Th2)both in serum and BALF in LPS group elevated significantly(Plt;0.01). PGE1 administration significantly decreased the ratio IFN-γ/IL-4 in serum after 6h(Plt;0.01)and in BALF at all time points(Plt;0.01).Conclusion The imbalance of was found in the LPS induced ALI,inhaled PGE1 aerosol inhalation could restore Th1/Th2 cytokine balance in the rats model induced by LPS.