4种5-HT4受体激动剂对大鼠心肌IK1通道的影响及促心律失常风险比较

摘要

目的 比较4种5-羟色胺4型(5-HT4)受体激动剂西沙必利(cisapride),扎考必利(zacopride),莫沙必利(mosapride)和2[1-(4-胡椒基)哌嗪]基苯并噻唑{2-[1-(4-Piperonyl) piperazinyl] benzothiazole,BZTZ}对大鼠心室肌细胞膜内向整流钾通道(IK1)功能和蛋白表达的影响,并观察其对大鼠离体心脏心律的影响,从而评估其致心律失常的风险.方法 应用全细胞膜片钳技术分别观察4种激动剂对胶原酶分解的成年SD大鼠心室肌细胞膜IK1和HEK293细胞异源表达的Kir2.1通道电流的影响.应用免疫印迹法检测4种激动剂孵育大鼠心室肌细胞24 h后IK1主要亚单位Kir2.1通道蛋白表达的变化.将麻醉大鼠的心脏取出进行Langendorff主动脉逆行灌流,分别观察4种激动剂给药30 min内离体心脏节律的变化,全程记录心电图.结果 在大鼠心室肌细胞,BZTZ,西沙必利和莫沙必利0.1 ～ 10μmol·L-1可浓度依赖性地抑制IK1.在相同浓度(1μmol·L-1)时,BZTZ对IK1的抑制效应最强(P＜0.01),其次为西沙必利,莫沙必利最弱.扎考必利可激动IK1(P＜0.01).在Kir2.1重组质粒转染HEK293细胞,扎考必利激动Kir2.1通道电流(P＜0.01),而莫沙必利无明显影响.在大鼠离体心脏,BZTZ和西沙必利1 μmol·L-1可引起严重的心律失常,期前收缩数分别达到159±28和(61±13)次(P＜0.01),室速发生率分别为50％ (P＜0.05)和25％,室颤发生率分别为37.5％和12.5％.莫沙必利和扎考必利对心律均无明显影响,不引起心律失常的发生.扎考必利还可抑制西沙必利和BZTZ诱发的心律失常.4种激动剂的促心律失常风险等级依次为BZTZ＞西沙必利＞莫沙必利和扎考必利.结论 IK1可能作为5-HT4受体激动剂致心律失常副作用的独立风险因子和筛选安全5-HT4受体激动剂和促胃肠动力药的新靶点.%OBJECTIVE To compare the effect of four 5-hydroxytryptamine type 4 (5-HT4) receptor agonists:cisapride,zacopride,macopride and 2-[1-(4-piperonyl) piperazinyl]-benzothiazole (BZTZ),on rat cardiac inward rectifier potassium channel (IK1)and heart rhythm.METHODS The whole-cell configuration of patch-clamp technique was used to record effects of 5-HT4 receptor agonists onIk1 in enzymatic dissociated rat ventricular myocytes or Kir2.1 transfected HEK 293 cells.Western blotting was used to observe the expression of Kir2.1 channel exposed 24 h to agents in ventricular myocytes.Langendorff-perfused hearts were perfused with four agents respectively for 30 min.The electrocardiogram was recorded simultaneously.RESULTS BZTZ,cisapride and mosapride 0.1-10 μmol· L-1 decreasedIk1 in a concentrationdependent manner.At the same concentration (1 μmol· L-1),BZTZ showed the most potent inhibition onIκ1 (P＜0.01),followed by cisapride.Mosapride showed slight inhibition efficiency.However,zacopride enhanced Iκ1 (P＜0.01).In Kir2.1 heterologous expression systems,zacopride activated Kir2.1 current (P＜0.01) while mosapride had no effect.In ex vivo Langendorff-perfused hearts,BZTZ and cisapride 1μmol· L-1 elicited singnificant rhythm disturbances,and the total of premature ventricular beats (PVB) were 159±28 and 61±13.50％ (4/8) (P＜0.05) and 25％ (1/8) of the hearts exhibited ventricular tachycardia (VT),while 37.5％ (3/8) and 12.5％ (1/8) of the hearts exhibited ventricular fibrillation (VF),respectively.Mosapride and zacopride had no side effects on heart rhythm.Zacopride also suppressed BZTZ-or cisapride-induced arrhythmias.BZFZ had the strongest proarryhthmic potency among the 5-HT4 agonists,followed by cisapride,mosapride and zacopride.CONCLUSION Iκ1 might be an independent risk factor for arrhythmogenesis and a new target for screening safe 5-HT4 receptor agonists and gastrointestinal prokinetic agents.