AIMThe present study described the effects of iptakalim and pinacidil, which belong to two different chemical structures of potassium channel opener (KCO), on mRNA expression for subunits of ATP-sensitive potassium channel (KATP), including SUR1, SUR2, Kir6.1, and Kir6.2.

METHODSReverse transcription-polymerase chain reaction (RT-PCR) using primers specific for these four subunit genes was performed on total RNA from rat tissues of heart, aortic smooth muscle and tail artery smooth muscle, after iptakalim and pinacidil administration for one week.

RESULTSCompared with the normal control group without drug administration, in heart tissue, iptakalim and pinacidil showed no significant effects on mRNA levels of the four subunits of KATP. In endothelium-free aortic smooth muscle, SUR2 mRNA level was up-regulated significantly in pinacidil group, while no subunits were changed by iptakalim treatment. In endothelium--free tail artery smooth muscle, Kir6.1 and Kir6.2 mRNA levels were reduced significantly in iptakalim group, and SUR2 and Kir6. 1 in pinacidil group.

CONCLUSIONThe gene expression patterns of KATP were different among tissues of heart, large artery and small artery. Iptakalim selectively down-regulated the mRNA levels of Kir6.1 and Kir6.2 in smooth muscle of small arteries, and the regulation effect of iptakalim on KATP was different from that of pinacidil in cardiovascular system.