摘要：AIM：The mechanism of tumor necrosis factor-alpha (TNF-α) induced pulmonary artery hypertension(PAH) in endotoxic shock (ES) is not clear. Cholecystokinin-octapeptide (CCK-8) had anti-ES and anti-PAH effects. The impact of CCK-8 on changes in vascular reactivity and endothelial ultrastructure induced by TNF-α was studied. The role of nitric oxide (NO) was preliminarily studied. METHODS：Rabbit pulmonary artery rings were divided into four groups: TNF-α, TNF-α+CCK-8, CCK-8 and Vehicle. The rings were incubated for 2 h, 7 h or 14 h. Relaxative responses to ACh(10-8-10-5 mol/L)， SNP (10-9-10-6 mol/L) and contractile responses to PE(10-8-10-5 mol/L) were generated seperately. The NOS activity of rings was detected and the ultrastructure of endothelium was observed in the groups that incubated for 7 h.RESULTS:The relaxative responses to ACh were not affected by TNF-α and CCK-8 after incubation for 2 h. TNF-α(7 h,14 h) significantly reduced ACh-induced endothelium-dependent relaxation response of pulmonary artery. CCK-8 reversed the effect. CCK-8 itself had no effect on responses of normal pulmonary artery. Contraction to PE and relaxation to SNP were unaffected by TNF-α, CCK-8. The NOS activity increased in the TNF-α and the TNF-α+CCK-8 groups. While no significant difference was obseved between the Vehicle and the CCK-8 groups. Endothelial injury in TNF-α group and alleviated changes in TNF-α+CCK-8 group were observed. CONCLUSION:TNF-α significantly inhibits endothelium-dependent relaxation, which be one of the mechanisms of PAH induced by TNF-α during ES. It was found for the first time that CCK-8 reversed TNF-α induced impairment of endothelium-dependent relaxation and alleviated structural injury of endothelium, which might be one of the mechanisms of anti-PAH effect by CCK-8 during ES. The effects of TNF-α and CCK-8 might be related to NO.