Selective actions of iptakalim on the subtypes of K_(ATP) channels / 中国药理学通报

ABSTRACT

Aim To establish a cell model heterologously expressing Kir6.x and SUR subunits of K_(ATP)channels and to study the selectivity of iptakalim on different subtypes of K_(ATP) channels.Methods Cell were transfected with the pcDNA vector containing the coding sequenced of Kir6.x and SUR using liposome and the pEGFP-N1 vector encoding for green fluorescent protein was added for easy identification of transfected cells.Using immunocytochemical technique,we detected the expression of Kir6.x and SUR protein in[FL(2K2]transfected cells.The electrophysiological experiment was performed after transfection 48-72 h.In whole cell configuration,the effects of K_(ATP) channel openers iptakalim,pinacidil and diazoxide on the clone currents in transfected HEK-293 cells and the antagonism of K_(ATP) channel inhibitor glibenclamide were evaluated.Results Immunocytochemical study identified the expression of Kir6.x and SUR protein in transfected cells.The electrophysiological experiment showed that in cells with recombinant expression of the Kir6.1/SUR2B channel complex,iptakalim(100 ?m),pinacidil(100 ?m)and diazoxide(200 ?m)significantly increased the clone current from(-88.0?30.8) pA to(-2042.6?127.3) pA,(-1431.9?142.4) pA and(-1104.7?228.9) pA,respectively,at-100 mV,and the actions were inhibited by glibenclamide(10 ?m).In cells expressed with Kir6.2/SUR2A channel,both iptakalim and pinacidil activated the currents,which was sensitive to glibenclamide.While diazoxide had no effects on the clone currents.In contrast,in cells with Kir6.2/SUR1channel,diazoxide increased the activity of recombinant K_(ATP) channels,while iptakalim and pinacidil had little effects.Conclusion From these observations,the effects of K_(ATP) channels openers with different chemical structures on the subtypes of K_(ATP) channels were diverse.Iptakalim showed selective action on Kir6.1/SUR2B and Kir6.2/SUR2A,but not Kir6.2/SUR1 K_(ATP) channels