Objective:To study the effect of Pinacidil on mRNA expression of ATP-sensitive K+(KATP) channels of primary cultured human pulmonary artery smooth muscle cells. Methods:Intrapulmonary arteries(3rd~4th division) were opened longitudinally. After removing the adventitia and epithelium by a blade,they were cut into pieces of 1~3 mm2. The tissue and smooth muscle cells were cultured with DMEM. Cells were incubated with test substances for 24 h by deviding into following groups:Control,ET-1 10 nmol/L,ET-1+Pinacidil 10 μmol/L,ET-1+Pinacidil 10 μmol/L+Glyburide 10 μmol/L. Total RNA was extracted by Trizol and reverse transcribed into cDNA. Real-time PCR was explored to measure the level of mRNA expression of KATP channels. Results:ET-1 suppressed expression of SUR2B mRNA of KATP channels for 0.09 ± 0.01-fold(P < 0.05,n = 3),compared with control group. Expressions of SUR2B mRNA in the group of ET-1+Pinacidil 10 μmol/L were 0.97 ± 0.03-fold(P > 0.05,n = 3) compared with control group. ET-1+Pinacidil 10 μmol/L+Glyburide 10 μmol/L were 0.07 ± 0.02-fold(P < 0.05,n = 3),compared with control group. There were no significant differences in the expression of Kir6.1 mRNA among all groups. Conclusion:Pinacidil increased the expression KATP channel SUR2B mRNA of primary cultured human pulmonary artery smooth muscle cells. This might be the mechanism in regulating mRNA expression of KATP channels in pulmonary arteries.