Objective:To investigate the effects of Iptakalim(IPT),a novel ATP sensitive potassium channel opener,on the lung mRNA expression of endothelin A receptor(ETAR)and endothelin B receptor(ETBR)in hypoxic pulmonary hypertension(HPH). Methods:SD rats were equally divided into normal-controlled group,HPH-model group,and IPT treated group(treated with IPT 1.5 mg/(kg·d) prior to hypoxia). The HPH-model group and IPT treated group were bred in normal baric and hypoxic condition,8 hours a day,6 days a week,for 4 weeks. Reverse transcription polymerase chain reaction(RT-PCR)was performed to analyze the expression of ETAR and ETBR. Results:The mRNA expression of ETAR was markedly higher(P < 0.01),whereas the level of ETBR mRNA was significantly lower in HPH rats than in control(P < 0.01);Iptakalim significantly inhibited the expression of ETAR mRNA(P < 0.01),and enhanced the expression of ETBR in HPH rats(P < 0.01). Conclusion:There were significantly alterations in gene expression of ET receptors in the lung of HPH,and Iptakalim could partly reverse this expression,which might contribute to inhibit vasoconstriction and vascular proliferation.