Objective:To investigate the effects of penehyclidine hydrochloride on apoptosis of lung tissue cells and its mechanism in acute lung injury following blunt chest trauma in rats.Methods:Sprague Dawley(SD)rats(n=54)weighing(250±25)g were divided equally and randomly into three groups:normal control group(C group,n=18),trauma model group(T group,n= 18)and penehyclidine hydrochloride treatment group(P group,n=18).Each group was further divided into three subgroups according to the time points of 3,12 and 24 hours after experiment(at each time point,n=6 for each subgroup).Rats of P group were intraperitoneally injected with penehyclidine hydrochloride for 2 mg/kg immediately after blunt chest trauma and rats in its 24 hours subgroup were once again injected with penehyclidine hydrochloride in the same dose 12 hours after injury.Lung tissue samples were collected at every time point and cell apoptosis in lung tissues were measured by TUNEL.Apoptotic index(AI)was calculated,expressions of bax and bcl-2 were detected by immunohistochemical staining of SABC,and lung tissue sections were taken for light and electron microscopic observation.Results:As compared with C group,at every time point,AI and expressions of bax and bci-2 in T group were higher(P＜0.05),and the ratio of bcl-2/bax markedly decreased(P＜0.05),especially in the 24 hours subgroup.The ratio in T group(0.468±0.007)was lower than that in C group (1.382±0.058,t=12.5,P＜0.01).Lung tissue injuries were significant under a light microscope,and the number of apoptotic cells increased obviously under a transmission electron microscope.As compared with T group at the same phase,AI and expression of bax decreased in P group(P＜0.05 and P＜0.01),while the expression of bcl-2 increased significantly(P＜0.01),and the ratio of bcl-2/bax markedly increased(P＜0.05),especially in the 24 hours subgroup.The ratio in P group(1.012±0.070)was much higher than that in T group(0.468±0.007,t=8.3,P＜0.01).The injury of lung tissues was relieved,and apoptosis of cells decreased obviously under a transmission electron microscopic observation.Conclusions:Apoptosis and expressions of bax and bcl-2 in lung tissues might be involved in the pathogenesis of lung injury induced by blunt chest trauma.Penehyclidine hydrochloride can alleviate lung injuries by inhibiting apoptosis of lung tissue cells,during which effects of penehyclidine hydrochloride on regulating expressions of bax and bcl-2 may play an important role.