埃他卡林对K_(ATP)通道亚型选择性作用的研究

目的建立特异性表达以K ir6.x和SUR亚单位组成的不同KATP通道亚型的细胞模型,研究KATP通道开放剂埃他卡林对KATP通道亚型的选择性作用特点。方法利用脂质体转染的方法将编码KATP通道亚单位K ir6.x-pcDNA3、SUR-pcDNA3基因和编码绿色荧光蛋白pEGFP-N1基因共同转染到HEK-293细胞中,免疫组化法鉴定细胞上K ir6.x和SUR蛋白的表达,并采用膜片钳全细胞记录技术,以KATP通道特异性激动剂吡那地尔和二氮嗪为对照,分析埃他卡林对特定刺激条件下对K ir6.x和SUR共同转染的细胞上诱发的钾电流的影响,并观察KATP通道特异性拮抗剂格列苯脲的阻断作用。结果在共同转入KATP通道两亚单位基因的HEK-293细胞上,有K ir6.x和SUR蛋白的表达。在共同表达K ir6.1/SUR2B的细胞上,埃他卡林(100μmol.L-1)、吡那地尔(100μmol.L-1)及二氮嗪(200μmol.L-1)均具有增强诱发电流的效应,给药前后-100 mV时电流值由(-88.0±30.8)pA分别增至(-2042.6±127.3)pA,(-1431.9±142.4)pA及(-1104.7±228.9)pA,三者的作用均能被格列苯脲所阻断。相同条件下,在共同表达K ir6.2/SUR2A的细胞上,埃他卡林和吡那地尔能增强诱发电流,此作用对格列苯脲敏感;而二氮嗪对该电流无影响。相反,在共同表达K ir6.2/SUR1的细胞上,二氮嗪能增强诱发电流,此作用对格列苯脲敏感;而埃他卡林和吡那地尔对该电流无影响。结论不同结构钾通道开放剂对不同亚型KATP通道作用不同,埃他卡林与吡那地尔作用相似,能选择性作用于K ir6.1/SUR2B和K ir6.2/SUR2A型KATP通道,对K ir6.2/SUR1型无影响。

Selective actions of iptakalim on the subtypes of KATP channels

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 inFL(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 μm),pinacidil(100 μm)and diazoxide(200 μm)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 μm).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