稳心颗粒甘松提取物对大鼠心室肌细胞钠电流和瞬时外向钾电流激活动力学的影响

目的研究步长稳心颗粒中甘松提取物对大鼠心室肌细胞钠电流(INa)、瞬时外向钾电流(Ito)激活动力学的影响。方法采用全细胞膜片钳技术,研究10 g/L甘松提取物对急性分离的成年大鼠心室肌细胞INa、Ito激活动力学的影响。结果①10 g/L甘松提取物使大鼠心室肌细胞INa峰值(INa,max)从-58.96±2.71 pA/pF降至-31.66±1.29 pA/pF(n=5,P<0.01);②10 g/L甘松提取物使Ito峰值(Ito,max)由3.40±1.52 pA/pF降到1.43±0.64 pA/pF(n=7,P<0.05)。10 g/L甘松提取物对INa和Ito的抑制率分别达38.2%和57.9%。结论10 g/L甘松提取物对大鼠心室肌细胞INa、Ito具有显著抑制作用。     

丹酚酸B对大鼠心室肌细胞瞬时外向钾电流和L型钙电流的阻滞作用

目的研究从丹参中分离提取的药物单体——丹酚酸B对大鼠心肌细胞上的瞬时外向钾电流(Ito)、内向整流钾电流(IK1)和L型钙电流(ICa,L)的电生理学作用。方法用酶解法分离大鼠心室肌细胞,全细胞膜片钳技术记录Ito、IK1和ICa,L。每个细胞采用加药前后自身对照,用含100μmol/L丹酚酸B的细胞外液灌流心室肌细胞,记录加药前、后的电流,所有数据均在细胞破膜后20min内完成。结果 100μmol/L的丹酚酸B对Ito和ICa,L具有抑制作用,使Ito和ICa,L最大激活峰值电流密度下降,电流密度-电压曲线下移;且丹酚酸B主要抑制Ito的快速电流成分Itof,而对Ito的缓慢电流成分Itos无明显作用。在60mV测试电压下,Itof的最大激活峰值电流密度从23.51±3.29pA/pF降为16.85±2.36pA/pF,抑制率为28.31%±10.6%(n=8,P0.05)。在-10mV测试电压下,100μmol/L丹酚酸B作用后ICa,L的最大激活峰值电流密度从-8.66±-2.40pA/pF降为-5.91±-2.14pA/pF,抑制率为31.84%±10.23%(n=11,P0.05)。丹酚酸B使Ito通道失活后的恢复减慢,但不改变ICa,L的通道动力学。丹酚酸B对IK1无显著作用。结论丹酚酸B对Ito和ICa,L具有阻滞作用,而对IK1无显著作用。     

犬Marshall韧带心肌细胞短暂外向钾电流的特性

目的　探讨Marshall束 (Marshallbundle ,MB)内心肌细胞短暂外向钾电流 (transientout wardpotassiumcurrent,Ito)的离子通道特性。方法　运用组织块酶解法分离犬MB内单个心肌细胞 ,在倒置显微镜下直接比较细胞形态 ;采用全细胞膜片钳技术记录MB内单个心肌细胞Ito电流密度及动力学特性。在细胞外液中加入 1μM异丙肾上腺素 ,比较加药前后Ito电流密度及动力学特性的变化。结果　MB内有两种形态迥异的心肌细胞 :一种为短矩形 ,短而宽 ,呈典型的矩形或略呈锥型 ;另一种为长杆型 ,长而窄。短矩形细胞数量明显多于长杆型细胞。短矩形细胞和长杆型细胞的长宽比分别为2 99± 0 95和 12 0 5± 2 4 1(P <0 0 1)。两种心肌细胞Ito的动力学无明显差别 ,但短矩形细胞的Ito电流密度明显小于长杆型细胞 ,8 77pA/pF (n =8)对 14 95 pA/pF (n =8) ,P <0 0 1。加用异丙肾上腺素后 ,在 70mV ,长杆型细胞Ito峰值减小到 7 96pA/pF (n =8) ;短矩形细胞减小到 3 89pA/pF(n =8) ;两种细胞加药后Ito分别减小 (5 0 4± 0 32 ) pA/pF和 (6 86± 0 4 9) pA/pF (P <0 0 5 ) ;稳态激活曲线均右移 ,短矩形细胞与长杆型细胞的V1/ 2 分别从 (- 7 1± 0 8)mV和 (- 6 8± 0 7)mV变为 (-1 8± 0 2 )mV和 (- 1 6± 0 4 )mV     

缬沙坦对血管紧张素Ⅱ引起人心房肌细胞离子电流改变的调节作用

目的:研究缬沙坦对血管紧张素Ⅱ(AngⅡ)引起人心房肌细胞离子电流改变的调节作用。方法:经典两步酶解法分离单个心房肌细胞,膜片钳全细胞法记录离子电流。结果:AngⅡ(300nmol/L)使快速内向钠电流(INa)从(-15.83±1.62)电流(pA)/电容(pF)降到(-6.35±1.83)pA/pF(P<0.01),其作用不能被缬沙坦(10μmol/L)抑制;使L型钙电流(ICa-L)从(-4.5±1.64)pA/pF增加到(-5.5±1.95)pA/pF(P<0.05),其作用能被缬沙坦抑制;指令电位-120mV时使内向整流性钾电流(IK1)从(-3.49±1.03)pA/pF增加到(-5.47±1.83)pA/pF(P<0.01),+10mV~+50mV时其外向电流成分随电压而增加,其作用不能被缬沙坦抑制。AngⅡ对超速激活延迟整流性钾电流(IKur)和瞬间外向钾电流(Ito1)无显著影响。结论:AngⅡ对人心房肌细胞ICaL有促进作用并可被缬沙坦抑制;增加IK1,抑制INa,其作用不能被缬沙坦抑制。     

血管紧张素Ⅱ对人心房肌细胞膜钾钙离子电流的作用

观察血管紧张素Ⅱ对人心房肌细胞膜主要离子流的作用,揭示其参与房性心律失常的细胞电生理机制。急性分离单个人心房肌细胞,采用全细胞膜片钳方法记录细胞膜短暂外向钾电流(Ito)、内向整流钾电流(Ik1)和L型钙电流(ICaL)。结果:0.1μmol/LAngⅡ使人心房肌细胞膜Ito峰值电流密度明显下降6.54±0.49pA/pFvs12.65±0.86pA/pF(P<0.05),在-100mV电压下使IK1峰值电流密度显著升高-8.93±1.12pA/pFvs-5.23±0.95pA/pF,(P<0.05),并明显促进人心房肌细胞膜ICaL-12.72±1.69pA/pFvs-5.79±0.84pA/pF(P<0.05)。结论:AngⅡ可促进人心房肌细胞膜IK1及ICaL,抑制人心房肌细胞膜Ito。     

BmkTXK β对家兔心房肌细胞钾电流的影响

为研究东亚钳蝎毒素BmkTXKβ对家兔心房肌单细胞电生理特征的影响 ,应用全细胞膜片钳技术记录各项钾电流和动作电位。结果 :BmkTXKβ呈浓度依赖性地延长动作电位时程 (APD2 0 、APD50 和APD90 ) ,但对动作电位幅度 (APA) ,静息膜电位 (RMP)和 0相最大除极速度 (Vmax)无明显影响 (n =9)。在刺激电压 +5 0mV时 1μmol/L的BmkTXKβ使心房肌细胞瞬间外向钾电流 (Ito)从 13.6 3± 0 .87pA/pF减少到 7.98± 0 .78pA/pF ,抑制率为 41.4%(n=10 ,P <0 .0 1)。同时 ,这种作用具有显著的浓度依赖性 ,抑制 5 0 %的电流所需浓度 (IC50 )的均值为 0 .95 μmol/L。BmkTXKβ可抑制延迟整流性钾电流 (IK) ,表现为剂量依赖性阻断的形式。 10 μmol/L时 (刺激电压 +70mV) ,它对IK的抑制率为 39.3 %(从 5 .86± 0 .6 4pA/pF降到 3 .5 6± 0 .5 8pA/pF ,n =6 ,P <0 .0 5 )。IC50 的均值为 2 .76 μmol/L。但BmkTXKβ对内向整流钾电流 (IK1)的电流幅值及其反转电位基本无影响 (n =6 ,P >0 .0 5 )。结论 :BmkTXKβ阻断Ito和IK 等与心脏复极相关的钾离子通道 ,且能在多个环节显著延长APD。     

Effects of simvastatin on Ion Channel Currents in ventricular myocytes from rabbit with acute myocardial infarction

Objective To investigate the effects of simvastatin on membrane ionic currents in left ventricular myocytes of rabbit heart suffering from acute myocardial infarction(AMI),so as to explore the ionic mechanism of statin treatment for antiarrhythmia. Methods Fourty-five New Zeland rabbits were randomly divided into three groups: AMI group, simvastatin intervention group (Statin group) and sham-operated control group (CON). Rabbits were infarcted by ligation of the left anterior descending coronary artery after administration of oral simvastatin 5 mg?kg-1?d-1 (Statin group) or placebo (AMI group) for 3 days. 24 h later, single ventricular myocytes were isolated enzymatically from the epicardial zone of the infracted region .Whole cell patch clamp technique was used to record membrane ionic currents, including sodium current (INa), L-type calcium current (ICa-L) and transient outward potassium current (Ito). Results There was not significant difference in serum cholesterol concentration among three groups. The peak INa current density(at –30 mV) was significantly decreased in AMI group (–23.26±5.18,n=12),) ompared with CON (–42.78±5.48 , n=16), P<0.05,while it was significantly increased in Statin group (–39.23±5.45 pA/pF, n=13) compared with AMI group, P<0.01;The peak ICa-L current density (at 0 mV) was significantly decreased in AMI group (–3.23±0.91 pA/pF, n=12) compared with CON (–4.56±1.01 pA/pF,n= 15),P<0.05,while it was significantly increased in Statin group (–4.18±0.95 pA/pF, n= 12) compared with AMI group, P<0.05; The Ito current density(at +60 mV) was significantly decreased in AMI group (10.41 ±1.93 pA/pF, n=12) compared with CON (17.41± 3.13 pA/pF , n=15), P<0.01, while it was significantly increased in Statin group (16.21 ± 2.42 pA/pF , n=13) compared with AMI group, P<0.01. Conclusions AMI induces significant down-regulation of INa, ICa-L and Ito pretreatment with simvastatin could attenuate this change without lowering the serum cholesterol level, suggesting that simvastatin could reverse this electrical remodeling, thus contributing to the ionic mechanism of statin treatment for antiarrhythmia .     

伊布利特对兔急性心肌梗死后梗死周边区心外膜心室肌细胞L型钙电流的影响

目的观察伊布利特对急性心肌梗死(AMI)后一周心室肌细胞L型钙通道电流(ICa-L)的影响。方法兔开胸,左前降支结扎造成AMI,1周后酶解分离梗死周边区心外膜心室肌细胞,用全细胞膜片钳技术记录10-6mol/L伊布利特细胞外液(伊布利特组)对梗死周边区心外膜心室肌细胞ICa-L活性的影响,并与正常对照组(对照组)及AMI但未灌流伊布利特组(AMI组)比较。结果①AMI 1周时兔梗死周边区心室肌细胞ICa-L受到抑制,电流密度-电压曲线(I-V)上移,ICa-L电流密度峰值降低[-3.52±0.91 pA/pF(n=10)vs-5.68±1.53 pA/pF(n=10),P<0.05];伊布利特组电流密度峰值为-4.84±1.22 pA/pF(n=8),较AMI组显著增大(P<0.05),与对照组比较,虽有减小,但无差异(P>0.05)。②AMI组、伊布利特组ICa-L失活曲线明显左移,以AMI组左移更加明显,对照组半数失活电压(V0.5)为-32±4 mV(n=10),AMI组V0.5增加为-46±7 mV(n=10,P<0.05),伊布利特组V0.5为-36±6mV(n=8),与对照组比较无差异(P>0.05)。结论AMI后1周梗死周边带心室肌细胞L型钙通道受阻滞,伊布利特对缺血引起的ICa-L的异常有明显改善作用。     

糖尿病对大鼠心肌细胞动作电位和瞬时外向钾电流的影响

目的探讨糖尿病对大鼠心室肌细胞动作电位(AP)和瞬时外向钾电流(Ito)的影响。方法通过链脲佐菌素诱导糖尿病大鼠模型,双酶法急性分离出对照组和糖尿病组心室肌细胞,全细胞膜片钳技术分别观察心肌细胞AP和Ito电流密度变化以及Ito动力学改变。结果与对照组比较,糖尿病组心肌细胞AP形态明显增宽,AP复极20%、50%和90%的时程均明显延长(64.3±7.5 ms vs 29.7±9.2 ms;174.3±6.8 ms vs 98.9±4.2 ms;276.7±8.3 ms vs 173.7±7.2 ms,P均<0.01,n=12);在钳制电位为+50mV时,与对照组比较,糖尿病组心肌细胞Ito的电流密度显著降低(11.51±1.37 pA/pF vs 17.43±1.98 pA/pF,P<0.05,n=12);与对照组比较,糖尿病组心肌细胞Ito的I-V曲线明显下移;失活曲线显著左移(P<0.01,n=12);失活恢复曲线明显减慢。结论糖尿病引起了心肌细胞AP时程延长,Ito幅度降低,并使Ito的失活加快以及失活后恢复减慢。     

增强型绿色荧光蛋白转染小鼠心脏后瞬时外向钾电流及钠钙交换电流的变化

目的探讨绿色荧光蛋白(GFP)转染对心脏瞬时外向钾电流(Ito)及钠钙交换电流(INCX)的影响。方法20只雄性小鼠等量随机分为对照组和增强型GFP(EGFP)组。EGFP组小鼠采用8点注射法均匀注射100μl腺病毒于左室游离壁上,对照组注射等量无菌生理盐水。一周后分离单个心室肌细胞,用膜片钳记录Ito及INCX。结果与对照组相比,EGFP组几乎所有测定电压下,Ito电流密度显著减小[如+60 mV时为8.40±1.55 pA/pF(n=9)vs 36.77±8.12 pA/pF(n=11),P<0.05]。INCX的前向模式不因转染EGFP变化[如-80 mV时为-0.35±0.05 pA/pF(n=8)vs-0.42±0.08 pA/pF(n=10),P>0.05],但反向模式电流显著增大[如+80 mV时为1.47±0.10 pA/pF(n=8)vs 0.72±0.05 pA/pF(n=10),P<0.05]。结论 EGFP转染可使心脏Ito显著减小,而INCX仅反向模式电流增大,其综合效应可能导致细胞内钙增加。     

胺碘酮对模拟缺氧状态下大鼠心室肌细胞瞬时外向和内向整流钾电流的影响

目的通过观察胺碘酮对模拟缺氧状态下急性分离的大鼠心室肌单细胞复极相中瞬时外向钾电流(Ito)和内向整流钾电流(IK1)通道的影响,探讨其在该条件下抗心律失常的作用机制。方法使用酶解法分离获取大鼠单个心室肌细胞,通过持续通以模拟缺氧细胞外液建立体外模拟缺氧模型,采用全细胞膜片钳实验技术研究胺碘酮对该条件下Ito和IK1的作用。结果胺碘酮呈剂量依赖性降低Ito和IK1电流幅值,对Ito抑制效应的起始浓度为1μmol/L,100μmol/L时抑制作用达最大,最大抑制幅度为56.78%±4.27%(23.98±2.18pA/pFvs10.38±4.27pA/pF;测试电压为+70mV;P<0.01;n=5),IC50(半数抑制浓度)为74.35μmol/L,但Ito的I-V曲线趋势并没有发生变化,稳态激活和失活曲线几乎不发生移动。胺碘酮对IK1内向电流部分抑制起始浓度为1μmol/L,外向电流部分抑制效应的起始浓度为2μmol/L,其最大抑制幅度分别为58.77%±10.76%(56.32±7.24pA/pFvs23.22±7.30pA/pF;测试电压为-150mV;P<0.01)和33.29%±2.15%(6.70±0.89pA/pFvs4.46±0.93pA/pF;测试电压为+40mV;P<0.01;n=5)。对内向电流成分的IC50为63.75μmol/L,IK1通道的稳态激活曲线无明显改变。结论在大鼠离体心室肌单细胞模拟缺氧条件下,胺碘酮对Ito和IK1电流幅度呈剂量依赖性抑制,有对抗缺氧本身造成的动作电位时程缩短效应;对I内向电流成分的敏感性高于外向成分。     

异丙肾上腺素对兔右心室心外膜下心肌细胞电生理机制的影响

目的文献报道一些Brugada综合征（Brugadasyndrome,BS）患者使用异丙肾上腺素（isoproterenol,Iso）能够减轻耵段抬高,抑制窒性心律失常和电风暴的发生。本文对Iso这一作用的细胞电生理机制进行研究。方法酶解法分离兔右心室外膜下心肌（sub-epieardium,Epi）细胞。采用全细胞膜片钳技术记录1μmol Iso作用前后动作电传（actionpotential,AP）、L型钙电流（L—typecalciumeH／TeRt,ICaL）及短暂外向钾电流（transient outward potassiumcurrent,Ito）的变化。结果①Iso显著延长动作电位时限（APD）;②Iso使Ito峰值从（11．4±1．7）pA／pF减少到（6．3±0．5）pA／pF（n=16,P〈0．05）,使Ito I—V曲线下移,稳态失活曲线左移及失活后恢复曲线右移;③Iso使ICaL峰值从（-6．1±0．6）pA／pF增加到（-8．64-0．9）pA／pF（n=10,P〈0．05）,使I—V曲线下移。结论Iso呈电压依赖性抑制Ito和增加ICaL,延长APD,这可能与Iso能够减轻BS患者ST段抬高,抑制Bs患者窄性心律失常和电风暴的发生有关。     

伊布利特对兔左室中层细胞L型钙电流的影响

目的观察伊布利特对正常心肌细胞L型钙通道电流(ICa-L)的影响。方法用全细胞膜片钳技术记录10-6,10-5mol/L伊布利特细胞外液对兔正常左室中层心肌细胞L型钙通道电流(ICa-L)活性的影响。结果①伊布利特灌流后ICa-LI-V曲线下移,低、高剂量伊布利特灌流后电流密度峰值明显增加(-8.34±2.67,-10.50±3.81pA/pFvs-5.68±1.53pA/pF,P均<0.01),且高剂量较低剂量灌流时增加更明显。②低、高剂量伊布利特灌流后失活曲线右移,且高剂量时右移更明显。高剂量时半数失活电压(V0.5)较低剂量和用药前显著降低,而低剂量与用药前无差异。三种状态的激活曲线无差异。结论伊布利特可能呈浓度依赖性影响心室肌细胞L型钙电流(ICa-L)活性。     

依那普利和厄贝沙坦及血管紧张素-(1-7)对快速心房起搏犬心房肌瞬时外向钾电流及L型钙电流的影响

目的研究依那普利、厄贝沙坦及血管紧张素-(1-7)[Ang-(1-7)]对快速心房起搏犬心房肌瞬时外向钾电流(Ito)、L型钙电流(ICa-L)及其基因表达的影响。方法普通杂种犬30只,分为假手术(S)组、心房起搏对照(C)组、依那普利(EN)组、厄贝沙坦(IB)组及Ang-(1-7)(A)组,每组6只。C组以特制起搏器维持500次/分右房起搏2周,S组安置起搏器但不予起搏刺激。EN组、IB组和A组,右房起搏同时分别给予依那普利、厄贝沙坦、Ang-(1-7)治疗至实验结束。观察心房肌细胞Ito、ICa-L和动作电位时程(APD)的变化,以及ItoKv4.3亚单位和ICa-Lα1C亚单位mRNA在心房组织的表达。结果与S组比较,心房起搏后,各刺激频率下C组和EN组APD复极达90%时程(APD90)显著缩短。IB组和A组,APD90缩短不显著。S组、IB组、A组,随着刺激频率增加APD90缩短,C组、EN组无此特征。除EN组外,不同刺激频率下,各组复极达50%时程(APD50)变化均不显著。与S组比较,C组、IB组Ito最大电流密度显著降低(P0.05),EN组显著升高(P0.01);C组、EN组、IB组ICa-L最大电流密度低于S组(P0.01)。C组、IB组Kv4.3mRNA转录水平低于S组(P0.01),EN组显著升高(P0.01)。C组、EN组、IB组、A组ICa-Lα1CmRNA转录水平较S组显著降低(P0.01)。结论依那普利、厄贝沙坦和Ang-(1-7)对快速心房起搏犬心房肌Ito、ICa-L及APD的影响不同。     

Ionic targets for drug therapy and atrial fibrillation-induced electrical remodeling: insights from a mathematical model.

Recent advances in molecular electrophysiology have made possible the development of more selective ion channel blockers for therapeutic use. However, more information is needed about the effects of blocking specific channels on repolarization in normal human atrium and in atrial cells of patients with atrial fibrillation (AF). AF-induced electrical remodeling is associated with reductions in transient outward current (Ito), ultrarapid delayed rectifier current (IKur), and L-type calcium current (ICa,L). Direct evaluation of the results of ion channel depression is limited by the nonspecificity of the available pharmacological probes. OBJECTIVES: Using a mathematical model of the human atrial action potential (AP), we aimed to: (1) evaluate the role of ionic abnormalities in producing AP changes characteristic of AF in humans and (2) explore the effects of specific channel blockade on the normal and AF-modified AP (AFAP). METHODS: We used our previously developed mathematical model of the normal human atrial AP (NAP) based on directly measured currents. We constructed a model of the AFAP by incorporating experimentally-measured reductions in Ito (50%), IKur (50%), and ICa,L (70%) current densities observed in AF. RESULTS: The AFAP exhibits the reductions in AP duration (APD) and rate-adaption typical of AF. The reduction in ICa,L alone can account for most of the morphological features of the AFAP. Inhibition of Ito by 90% leads to a reduction in APD measured at -60 mV in both the NAP and AFAP. Inhibition of the rapid component of the delayed rectifier (IKr) by 90% slows terminal repolarization of the NAP and AFAP and increases APD by 38% and 34%, respectively. Inhibition of IKur by 90% slows early repolarization and increases plateau height, activating additional IK and causing no net change in APD at 1 Hz in the NAP. In the presence of AF-induced ionic modifications, IKur inhibition increases APD by 12%. Combining IKur and IKr inhibition under both normal and AF conditions synergistically increases APD. In the NAP, altering the model parameters to reproduce other typical measured AP morphologies can significantly alter the response to K(+)-channel inhibition. CONCLUSIONS: (1) The described abnormalities in Ito, IKur and ICa,L in AF patients can account for the effects of AF on human AP properties; (2) AP prolongation by IKur block is limited by increases in plateau height that activate more IK; (3) Blockers of IKur may be more effective in prolonging APD in patients with AF; 4) Inhibition of both IKur and IKr produces supra-additive effects on APD. These observations illustrate the importance of secondary current alterations in the response of the AP to single channel blockade, and have potentially important implications for the development of improved antiarrhythmic drug therapy for AF.     

The ionic mechanisms of long QT interval in diabetic rabbits

Objective Abnormal QT prolongation associated with arrhythmias is considered the major cardiac electrical disorder and a significant predictor of mortality in diabetic patients. The precise ionic mechanisms for diabetic QT prolongation remained unclear. The present study was designed to analyze the changes of ventricular repolarization and the underlying ionic mechanisms in diabetic rabbit hearts. Methods Diabetes was induced by a single injection ofalloxan （145mg/kg, Lv. ）. After the development of diabetes （10 weeks）, ECG was measured. Whole-cell patch-clamp technique was applied to record the action potential duration （APD50, APD90）, slowly activating outward rectifying potassium current （IKs）, L-type calcium current （ICa-L） and inward rectifying potassium current （IK1）. Results The action potential duration （APD50 and APD90） of ventricular myocytes was obviously prolonged from 271.5＋32.3 ms and 347.8＋36.3 ms to 556.6~72.5 ms and 647.9~72.2 ms respectively （P〈 0.05）. Meanwhile the normalized peak current densities of IKs in ventricular myocytes investigated by whole-cell patch clamp was smaller in diabetic rabbits than that in control group at test potential of＋50mV （1.27~0.20 pA/pF vs 3.08~0.67 pA/pF, P〈0.05）. And the density of the ICa-L was increased apparently at the test potential of 10 mV （-2.67~0.41 pA/pF vs -5.404-1.08 pA/pF, P〈0.05）. Conclusion Ventricular repolarization was prolonged in diabetic rabbits, it may be partly due to the increased L-type calcium current and reduced slow delayed rectifier K＋ current （IKs） （J Geriatr Cardio12010; 7：25-29）.     

兔上腔静脉肌袖细胞动作电位及L型钙电流特征

研究兔上腔静脉肌袖细胞(SVCM)动作电位和L型钙电流(ICa,L)特征及异丙肾上腺素(Iso)对其影响。通过全心灌流酶解方法来分离兔SVCM,利用全细胞膜片钳技术,记录10nmol/LIso干预前后SVCM及右房心肌细胞(RAM)的动作电位、钙电流。结果:与RAM比较,SVCM动作电位复极50%时间(APD50),复极90%时间(APD90)明显要长(175.11±8.21msvs77.78±7.74ms,354.39±16.40msvs173.69±11.44ms,P均<0.05),Iso明显延长两者动作电位时程。SVCMICa,L较RAM大(4.04±0.74pA/pFvs2.75±0.33pA/pF,P<0.05),Iso明显增加ICa,L峰值,SVCMICa,L变化较RAM明显(4.04±0.74pA/pFvs7.14±0.77pA/pF;2.75±0.33pA/pFvs4.72±0.86pA/pF,P<0.05)。结论:SVCM动作电位及钙离子通道与RAM存在差异,可能是触发或驱动局灶性心房颤动的基础,Iso在其中发挥重要的作用。     

替米沙坦对牵张刺激乳大鼠心房肌细胞短暂外向钾电流和动作电位的影响

目的探讨替米沙坦对牵张刺激乳大鼠心房肌细胞瞬时外向钾电流（Ito）和动作电位（AP）的影响。方法利用胰酶与Ⅱ型胶原酶混合酶解,并结合差速贴壁和5-溴脱氧尿嘧啶核苷处理得到纯化的乳大鼠心房肌细胞。实验分对照组、牵张组、替米沙坦（1μmol/L）组。采用全细胞膜片钳技术分别记录三组Ito和AP。结果在＋20~＋60 mV刺激电压水平,Ito电流密度（pA/pF）：牵张组低于对照组[＋20 mV和＋60 mV分别为（0.8±0.3）vs（2.1±0.8）和（1.6±0.4）vs（12.1±3.0）;P均〈0.01],替米沙坦组[＋20 mV和＋60 mV分别为（1.4±0.3）和（6.7±1.3）较牵张组增大,P均〈0.01]。牵张组AP复极50%、90%时程（APD50、APD90）较对照组明显缩短[（9.6±1.3 ms）vs（15.5±2.4）ms,（29.9±2.9）ms vs（56.3±3.6）ms,P均〈0.01,n=9],替米沙坦组[APD50、APD90分别为（11.7±2.0）和（41.4±4.6）ms]较牵张组APD延长（P均〈0.05）。结论牵张刺激可降低乳大鼠心房肌细胞Ito电流密度、缩短APD;替米沙坦干预可抑制牵张刺激的此作用。     

正常大鼠心室肌细胞动作电位和瞬时外向钾离子流的特点

目的研究正常Spraque-Dawley大鼠外层、中层和内层心室肌细胞动作电位(AP)和瞬时外向钾离子流(Ito)的特点。方法采用酶消化法获得大鼠外层、中层和内层心室肌细胞,以全细胞膜片钳技术记录心室肌细胞AP和Ito。结果成功记录到大鼠心室肌细胞外、中和内层心肌细胞AP和Ito。外层至内层心室肌细胞动作电位时程(APD)逐渐延长(P<0.05)。在+70mV刺激时外层至内层心室肌细胞Ito电流密度逐渐减小,分别为59.50±15.99,29.15±5.53和12.29±3.62pA/pF(P<0.05)。三层心室肌细胞曲线半激活电压、半失活电压及失活后恢复时间均无差异(P>0.05)。结论大鼠三层心室肌细胞AP形态和Ito大小存在分层差别。