objective: to investigate the effect of iptakalim(ipt),a novel atp sensitive potassium(katp) opener,on the expression of proliferating cell nuclear antigen (pcna) mrna in primary cultured human pulmonary artery smooth muscle cells. methods:under germfree conditions,the smooth muscular layers were separated from human pulmonary arterioles(3rd~4th divisions). human pulmonary artery smooth muscle cells were cultured by tissue block method and were divided into following groups:control group,hypoxia group,hypoxia+iptakalim or pinacidil group and hypoxia+iptakalim or pinacidil+glibenclimide group. fluorescence quantitative reverse transcription-polymerase chain reaction(fq-rt-pcr)was used to measure the expression level of pcna mrna. results:the expression of pcna mrna in hypoxia group increased(3.90±0.24) times higher than that in control group. ipt at the concentrations of 10-7,10-6 and 10-5 mol/l lowered the expression of pcna mrna by (26.00±2.01)%,(55.33±4.04)%,(79.00±1.00)%,respectively,compared with that in hypoxia group(p < 0.01). glibenclimide (gli) at the concentration of 10-5 mol/l antagonized the effect of ipt with the same concentration on the expression of pcna mrna,compared with that in hypoxia + ipt 10-5 mol/l group(p < 0.01). conclusion:the expression of pcna mrna in human pulmonary artery smooth muscle cells under hypoxic conditions increased,while ipt has an inhibitory effect on the expression of pcna mrna in a concentration-dependent manner through activating katp channels.