目的:观察和探讨内向整流钾通道(IK1)激动剂盐酸扎考必利(zacopride,Zac)对异丙肾上腺素(isoproterenol,Iso)所致心室重构的影响及作用机制.方法:SD大鼠随机分为正常对照组、Iso模型组、Zac干预组、Zac+氯喹干预组和卡托普利阳性对照组.腹腔注射异丙肾上腺素3 mg/kg,每天1次,连续给药10 d,观测各组全心质量/体质量比和左心室质量/体质量比.用全细胞膜片钳技术检测大鼠心室肌细胞电压门控钙电流(ICa-L)、静息膜电位(RMP)及动作电位时程(APD)的变化.选用新生1~3 d的SD乳鼠,用0.08%胰蛋白酶和0.04%Ⅱ型胶原酶消化心脏组织,经差速贴壁法和5-溴脱氧尿嘧啶核苷纯化心肌细胞后随机分成正常对照组、Iso模型组、Zac干预组、Zac+BaCl2干预组和Zac+氯喹干预组,培养24 h后用激光共聚焦显微镜检测心肌细胞内游离钙离子浓度.结果:Iso模型组与正常对照组比较,全心肥厚指数、左心室肥厚指数明显增加,膜片钳结果提示RMP减小,APD明显延长;Zac干预组明显抑制心肌肥大,并增大RMP,缩短APD.同时应用低剂量IK1抑制剂氯喹可明显抑制Zac的抗心室重构作用,并逆转Zac对RMP和APD影响.在乳鼠心肌细胞,Iso可使细胞表面积增大,细胞内[Ca2+]i增高;Zac干预后细胞形态恢复至正常或接近正常水平,并显著减轻钙超载.IK1阻断剂BaCl2和氯喹可阻断Zac的效应.结论:IK1选择性激动剂Zac明显抑制异丙肾上腺素所致的心室重构,其机制可能为增强IK1,进而增大RMP,缩短APD,从而阻断心肌细胞内钙超载依赖的信号通路.%AIM: To investigate the effect of inward rectifier potassium channels ( IK1 ) agonist zacopride on isoproterenol ( Iso)-induced ventricular remodeling and the involved mechanisms .METHODS:SD rats were randomly di-vided into 5 groups: control, Iso model, Iso+zacopride, Iso+zacopride +chloroquine and Iso +captopril groups.The model of cardiac hypertrophy was developed by intraperitoneal injection of Iso (3 mg· kg-1 · d-1 for 10 d) and verified by determination of heart-to-body weight ratio and left ventricle-to-body weight ratio .The changes of voltage-gated calcium cur-rent (ICa-L), resting membrane potential (RMP) and action potential duration (APD) of the rat ventricular myocytes were detected by the technique of whole-cell patch clamp.Neonatal rat cardiomyocytes were isolated by 0.08% trypsin and 0. 04%type II collagenase , and purified using differential adherence method and 5-bromodeoxyuridine .Cultured neonatal rat cardiomyocytes were randomly divided into 5 groups: control, Iso, Iso +zacopride, Iso +zacopride +BaCl2 and Iso +zacopride+chloroquine groups .After harvested for 24 h, the [ Ca2 +] i of the cardiomyocytes was recorded using a laser confocal scanning microscope .RESULTS:Compared with control group , the whole heart hypertrophic index and left ven-tricular hypertrophic index in Iso group were increased significantly (P<0.01).Patch clamp data suggested that RMP was reduced , and APD was obviously prolonged .Zacopride treatment obviously inhibited myocardial hypertrophy , increased the RMP and shortened APD (P<0.01).At the same time, application of low dose of I K1 atagonist chloroquine reversed the effect of zacopride .In cultured neonatal rat cardiomyocytes , Iso increased the cell area and [ Ca2 +] i .Zacopride treatment restored the hypertrophic morphology of the cells to normal or nearly normal levels , and significantly attenuated calcium overload.IK1 blocker, BaCl2 or chloroquine, reversed the effect of zacopride .CONCLUSION:IK1 agonist zacopride signif-icantly inhibits left ventricular remodeling caused by isoproterenol .Via enhancing I K1 , thereafter increasing RMP and shor-tening APD, zacopride might decrease Ca 2+influx and inhibit intracellular calcium overload-dependent signaling pathway .
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