Aim To explore the relationship between apoptosis in lung tissues and lung ischemia-reperfusion injury,and observe effects of safflower injection on pneumocyte apoptosis in lung ischemia-reperfusion injury.Methods Single lung in situ ischemia reperfusion animal model was used.84 rabbits were randomly divided into control group(C),ischemia/reperfusion 1 h group(IR1h),IR3h,IR5h,safflower injection 1 h group(SI1h),SI3h and SI5h.TdT mediated dUTP nick end labeling(TUNEL),electron microscope,immunocytochemistry and in situ hybridization(ISH) techniques were used to observe apoptosis,pulmonary ultrastructure and Bcl-2,Bax expression respectively in lung tissues of different group rabbits.Results Compared with control group,cell apoptosis,Bcl-2,Bax expression were up-regulated in lung tissues of IR groups(all of p<0.01).The safflower injection susppressed apoptosis as well as expression of Bax,but which improved the expression of Bcl-2 gene and the ratio of Bcl-2/Bax at the same time(p<0.01 or p<0.05,respectively).Electron microscope showed serious pulmonary ultrastructure damage in IR group,but no significant injury was found in SI group.There was a significant positive correlation between AI and Baxprotein,BaxmRNA(r=0.926,0.913;p<0.01,respectively),and there was a significant negative correlation between AI and the ratio of Bcl-2protein/Baxprotein,Bcl-2mRNA/BaxmRNA(r=-0.367,-0.375;p<0.01,respectively).Conclusion Apoptosis participates in lung ischemia reperfusion injury.The protective effects of safflower injection include suppressing the expression of Bax,blocking pneumocyte apoptosis and promoting Bcl-2 expression and the ratio of Bcl-2/Bax in lung ischemia-reperfusion injury.