Background Organophosphate poisoning is an important health problem in developing countries which causes death mainly by inducing acute lung injury.In this study,we examined the effects of penehyclidine hydrochloride (PHC),a selective M-receptor inhibitor,on dichlorvos-induced acute lung injury in swine.Methods Twenty-two female swines were randomly divided into control (n=5),dichlorvos (n=6),atropine (n=6),and PHC (n=5) groups.Hemodynamic data,extravascular lung water index (EVLWI),and pulmonary vascular permeability index (PVPI) were monitored; blood gas analysis and acetylcholinesterase (AchE) levels were measured.PaO2/FiO2,cardiac index (Cl),and pulmonary vascular resistance indices (PVRI) were calculated.At termination of the study,pulmonary tissue was collected for ATPase activity determination and wet to dry weight ratio (W/D) testing 6 hours post-poisoning.TUNEL assay,and Bax,Bcl-2,and caspase-3 expression were applied to pulmonary tissue,and histopathology was observed.Results After poisoning,PHC markedly decreased PVRI,increased CI more effectively than atropine.Anticholinergic treatment reduced W/D,apoptosis index (AI),and mitigated injury to the structure of lung; however,PHC reduced AI and caspase-3 expression and improved Bcl-2/Bax more effectively than atropine.Atropine and PHC improved ATPase activities; a significant difference between groups was observed in Ca2+-ATPase activity,but not Na+-K+-ATPase activity.Conclusions The PHC group showed mild impairment in pathology,less apoptotic cells,and little impact on cardiac function compared with the atropine group in dichlorvos-induced acute lung injury.