缺氧对豚鼠心室肌细胞快钠电流的影响

应用膜片钳全细胞技术研究缺氧对急性分离的豚鼠心室肌细胞快钠电流(INaT)的影响。结果表明,缺氧可减小豚鼠心室肌细胞INaT,且呈时间及电压依赖性,缺氧15min时,INaT平均电流密度由对照值(47.36±7.26)pA/pF减小到(36.07±5.58)pA/pF(n=6,P<0.05)。提示缺氧对心室肌细胞INaT的抑制作用可能明显延缓兴奋在心内的传导,从而在缺血性心律失常的发生中起重要作用。     

“解心痛”煎剂对蟾蜍心室肌细胞电活动的影响

本文报告了以5%浓度的“解心痛”对心室肌细胞电活动参数的影响。经“解心痛”处理后的心室肌细胞,其静息膜电位基本保持原水平,动作电位振幅、0相最大除极化速率,膜反应性和传导性均下降,2相平台缩短,复极化速率减低,动作电位完全复极化时程缩短,而有效不应期反有延长。对“解心痛”抗心律失常的可能机制进行了讨论。     

碘化N-正丁基氟哌啶醇对大鼠缺氧复氧心肌细胞钠钙交换体电流的抑制作用

碘化N-正丁基氟哌啶醇(N-n-butyl haloperidol iodide,F2)为本研究室改造合成的新化合物。前期研究发现F2作为L-型钙通道拮抗剂,能剂量依赖地拮抗缺血再灌注所导致的大鼠心脏损伤。研究F2对缺氧复氧(hypoxia/reoxygenation,H/R)大鼠心肌细胞钠钙交换体电流的作用并探讨其保护机制。采用Langendorff灌流系统灌流SD大鼠心脏,标准酶解法消化分离得到单个心室肌细胞。正常台式液灌流5min,立即灌流充90%N2-10%CO2的缺氧液,建立体外心肌细胞H/R模型,采用全细胞膜片钳技术记录对照、模型以及不同浓度F2(0.1、1、10μmol/L)对心肌细胞钠钙交换体电流,观察H/R状态F2对心肌细胞钠钙交换体电流的影响。结果显示:缺氧抑制钠钙交换体电流主要是抑制外向电流;H/R引起钠钙交换体电流增大,尤其是外向电流的增大。F2呈浓度依赖地抑制钠钙交换体电流,钠钙交换体电流I-V曲线上移。以上表明:F2能抑制钠钙交换体电流,尤其是外向电流,防止H/R时心肌细胞的钙超载,保护心肌细胞。     

钙离子对经低温处理的心室肌细胞电活动的影响

用玻璃微电极进行细胞内记录,观察了灌流液中钙离子浓度的变化对经低温处理的猪心室肌细胞电活动的影响。经低温处理的心室肌细胞对钙离子的反应与新鲜标本相似。当灌流液中缺钙时,心室肌细胞只产生局部反应,表明钙离子在经低温处理的心室肌细胞电活动中是不可缺少的。高钙的影响主要表现为动作电位复极的变化和兴奋阈值的增大。在高钙作用下,经低温处理的心室肌细胞未出现舒张期自动去极化或振荡电位,无自发性节律电活动出现,说明经低温处理,猪心室肌细胞不能用高钙的方法触发节律活动。本实验结果支持以前的推测,即长时间低温处理的心室肌,其节律活动与触发性活动不同,而具有自动性活动的特点。     

苦参总硷对猪心室肌动作电位的影响

用24只猪心研究了心室肌细胞电活动的特点及苦参总硷对心室肌动作电位的影响。用玻璃微电极记录的动作电位表明,在动作电位幅度、动作电位时间以及有效不应期等方面与其他哺乳动物的特点相似,只有dv/dt max较低。药物实验表明,苦参总硷能降低动作电位幅度及dV/dt max,能延长动作电位时间及有效不应期,这些作用与奎尼丁很相似。因此设想,苦参总硷抗心律失常的作用机制类似奎尼丁。苦参总硷中的有效成分是熔点低的生物硷,可能是苦参硷或苦参烯硷,而熔点高的氧化苦参硷及苦参醇硷对心室肌动作电位无明显作用。     

长时间冷处理后猪心室肌细胞对电刺激的反应

用13个猪心观察了经低温处理(24—72小时)后,在诱发节律活动过程中及出现节律活动后,心室肌细胞对不同频率电刺激的反应。当心室肌细胞的电刺激只能发生局部反应时,在一定范围内,较慢频率(2秒1次)的电刺激比较快的频率(1秒1次)能更快地引起可传播的动作电位,而更高频率的刺激则使局部反应明显抑制。在每秒1次的驱动刺激下,可传播的动作电位逐渐产生超极化和后去极化。对每秒2次或更快的刺激心室肌能发生反应,但超极化及后去极化并不加强。在节律活动产生以后,无论低膜电位或高膜电位节律活动,对高频率电刺激均能发生超动阻抑。抑制的程度与节律活动的频率有关,也与刺激频率及持续时间有关。当刺激频率固定时,节律活动越快,即与刺激频率相差越小时,抑制越弱,反之则越强。刺激持续时间越长则抑制作用也越大。以上结果表明,低温处理后由电刺激诱发的心室肌细胞节律活动近似起搏细胞正常活动的特点,而与以振荡电位为基础的触发性节律活动不同。     

抗心律失常药物作用最佳靶点研究

目的:通过研究乌头碱、哇巴因致心律失常作用的离子靶点,揭示抗心律失常药物作用的最佳靶点。方法:采用全细胞膜片钳技术研究乌头碱、硅巴因对大鼠单个心室肌细胞动作电位时程(APD)、L-型钙电流(ICa)、钠电流(INa)、内向整流钾电流(IK1)以及瞬时外向钾电流(Ito)的作用。结果:乌头碱(1μM)使大鼠单个心室肌细胞90%复极化动作电位时程(APD90)从给药前的150.23±7.02ms延长至236.03±23.22ms(n=8,p<0.01)。ICa在0mV刺激电位下从-727.9±178.0pA增加至-1082.1±222.2pA(n=6,p<0.01);IK1在-110mV刺激电位下从-2122.0±511.1pA增加到-2536.3±386.5pA;乌头碱(1μM)抑制Ito,在+50mV刺激电压下,Ito从3203.6±617.1pA下降到2809.0±547.3pA。同时增加INa。哇巴因5μM使大鼠心肌细胞APD缩短(APD90从86.3±25.2ms缩短至58.9±20.8msn=5,p<0.01),ICa在+10mV刺激电位下从-1326.9±318.9pA减少到-782.3±395.3pA;使Ik1从-1868.3±187.8pA增加到-2392.8±366.7pA(刺激电压-120mV,n=10,p<0.01);使Ito从1272.7±317.6pA增加到1706.6±485.5pA(刺激电压+60mV,n=5,p<0.01)。结论:乌头碱、哇巴因诱发心律失常发生的活性点或最佳靶点是ICa,INa,IK1,Ikr和Iks。APD缩短或过度延长均可致心律失常,一个理想的抗心律失常药物应对心     

一种快速可靠的豚鼠心室肌细胞分离法

报道一种快速的豚鼠心室肌细胞分离方法。该方法可获得杆状、清晰边缘的耐Ca^2 的单个心室肌细胞。     

过量运动对大鼠心肌细胞钙离子通道的影响

研究过量运动对心室肌细胞钙离子通道的影响,旨在进一步探讨其在心肌损伤中的意义。制备离体心室肌细胞并用去甲肾上腺素（NE）诱导建立类似过量运动所产生的应激心肌细胞模型,应用流式细胞术（FCM）和Fura2荧光分光光度法测定应激心室肌细胞的凋亡率和心肌细胞内游离钙浓度变化。实验组心肌细胞异常活动可能导致钙超载,从而引起心肌细胞凋亡,导致应缴性心肌损伤的发生。     

基于修订的心室肌细胞模型的短QT综合征病理仿真

基于已公布的人体心室肌细胞模型数据建立了一维心室肌细胞模型,仿真了伪心电图及心内膜细胞、心中间膜细胞和心外膜细胞这三种细胞的动作电位.基于构建的模型进行周期实验,针对实验中出现的问题修订模型中的参数.将修订后模型的仿真结果与已经公布的实验数据进行对比,从而验证模型修订的合理性和可靠性.最后基于修订的心室肌细胞模型对与KCNJ2有关的短QT综合征的病理情况进行仿真,分析仿真结果,验证了修订模型的实用性.     

Effect of La^3＋ on myocardiac potassium channels revealed by patch-clamp technique

The effect of La^3 on potassium channels in rat ventricular myocytes was investigated using the whole-cell patch-clamp recording mode. The Ca^2 -independent voltage-activated outward K~ current was activated by the depolar-izing pulse in enzymatically isolated rat ventricular myocytes. After addition of different concentrations La^3 to the bath solution, the outward K^ current was depressed gradually. The inhibition effect was in a concentration-dependent manner. The phenomena of the outward K^ current, being themain repolarizing current suppressed by La^3 , suggest that the effect of lanthanides on myocardial function should be exploited further.     

三七总皂苷对心梗后心室重构大鼠增强抗氧化与改善心肌形态学作用

 为研究三七总皂苷(PNS)对急性心肌梗塞（AMI）后左室重构（LVRM）大鼠自由基损伤和心肌细胞形态学改变的作用, 采用结扎大鼠左冠状动脉前降支的方法,建立AMI模型,术后24 h后随机分为对照组和实验组,连续4周分别灌胃给予生理盐水和PNS低、中、高剂量,观察PNS和福辛普利对病鼠血清丙二醛（MDA）、c反应蛋白(CRP)、肌红蛋白-I（cTn-I）及肌酸激酶同工酶（CK-MB）、谷胱甘肽过氧化物酶（GSH-Px）、一氧化氮（NO）及心肌细胞形态病理结构和心脏指数改变等的影响。结果发现与对照组比较,PNS与福辛普利均能显著改善病鼠左室心肌细胞形态结构病理改变及心脏指数（P<0.01）,显著降低MDA、CRP、CK-MB与cTn-I、提高GSH-Px活性（P<0.01～0.05）,高剂量PNS可明显降低NO含量（P<0.05）。可见PNS可通过抑制脂质过氧化反应,减轻病鼠心肌细胞的病理损伤,增强抗氧化,具有抑制心肌肥大与改善心室重构心肌细胞形态学结构作用。     

心室除极过程计算机模拟模型

建立了正常人心室的三维计算机模型,包括心室肌单元划分、心室肌单元电活动模型、传导系统、兴奋传播规律。从极化场出发导出了心室除极向量的数学表达式。运用上述模型、公式模拟了心室除极过程的心电向量图。     

Study of transmembrane La3+ movement in rat ventricular myocytes by the patch-clamp technique

We have studied transmembrane La3+ movement in rat ventricular myocytes for the first time by using the whole-cell patch-clamp recording mode. La3+ (0.01-5.0 mmol/L) could not bring out inward currents through the L-type calcium channel in rat ventricular myocytes, while it could enter the cells by the same way carried by 1μmol/L ionomycin. When the outward Na+ concentration gradient is formed, La3+ can enter the cells via Na-Ca exchange, and the exchange currentsincrease with the increase of external La3+ concentrations. But compared with Na-Ca exchange currents in the same concentration, the former is only 14%-38% of the latter. The patch-clamp experiment indicates that La3+ normally can not enter ventricular myocytes through L-type calcium channel, but it can enter the cells via Na-Ca exchange.     

Kinetics, stoichiometry and role of the Na-Ca exchange mechanism in isolated cardiac myocytes

Compelling evidence has existed for more than a decade for a sodium/calcium (Na-Ca) exchange mechanism in the surface membrane of mammalian heart muscle cells which exchanges about three sodium ions for each calcium ion. Although it is known that cardiac muscle contraction is regulated by a transient increase in intracellular calcium ([Ca2+]i) triggered by the action potential, the contribution of the Na-Ca exchanger to the [Ca2+]i transient and to calcium extrusion during rest is unclear. To clarify these questions, changes in [Ca2+]i were measured with indo-1 in single cardiac myocytes which were voltage clamped and dialysed with a physiological level of sodium. We find that Ca entry through the Na-Ca exchanger is too slow to affect markedly the rate of rise of the normal [Ca2+]i transient. On repolarization, Ca extrusion by the exchanger causes [Ca2+]i to decline with a time constant of 0.5 s at -80 mV. The rate of decline can be slowed e-fold with a 77-mV depolarization. Calcium extrusion by the exchanger can account for about 15% of the rate of decline of the [Ca2+]i transient (the remainder being calcium resequestration by the sarcoplasmic reticulum (SR]. The ability of the cell to extrude calcium was greatly reduced on inhibiting the exchanger by removing external sodium, which itself led to an increase in resting [Ca2+]i. This finding is in contrast to the suggestion that calcium extrusion at rest is mediated mainly by a sarcolemmal Ca-ATPase.(ABSTRACT TRUNCATED AT 250 WORDS)     

心肌Na+-Ca2+ 交换和缺氧-复氧

心肌细胞Na^ -Ca^2 交换在缺氧．复氧条件下通过Na^ -H^ 交换、持续性钠电流等途径使胞内Na^ 升高，进而在去极的静息膜电位、氧自由基共同作用下促进反向的Na^ -Ca^2 交换，导致胞内Ca^2 超栽。Ca^2 超栽引起心肌再灌注损伤、心律失常的发生和细胞高度挛缩甚至死亡。深入研究和探讨缺氧．复氧时Na^ -Ca^2 交换导致心肌损伤的机理，对于研发临床用于心肌保护的药物有重大意义和广阔前景。     

An isoprenaline activated sodium-dependent inward current in ventricular myocytes

In the heart, catecholamines affect pacemaker activity by shifting the activation curve for the nonspecific inward current and increasing both the calcium current, and the delayed potassium current. We report here that in mammalian ventricle there is another mechanism that seems to involve a sodium-dependent inward current. This is elicited by agents that increase intracellular cyclic AMP concentration, such as the beta-adrenergic agonist isoprenaline, and is unaffected by agents which block the three currents listed above, but is absent when external sodium is replaced with tetramethylammonium. Most interestingly, the intracellular pathway(s) linking the beta-receptor(s) to activation of the Ca current and the Na-dependent current, which in both cases presumably involves the intracellular concentration of cAMP, differ, as isoprenaline causes a persistent augmentation of the calcium current whereas the Na-dependent current often fades. These effects of isoprenaline are antagonized by acetylcholine. In unclamped cells, the Na-dependent current depolarizes the membrane to the potential range at which repetitive firing occurs. It may therefore be involved in the generation of ventricular arrhythmias.     

The protein kinase A-regulated cardiac Cl- channel resembles the cystic fibrosis transmembrane conductance regulator.

Stimulation of beta-adrenoceptors in cardiac ventricular myocytes activates a strong chloride ion conductance as a result of phosphorylation by cyclic AMP-dependent protein kinase (PKA). This Cl- conductance, which is time- and voltage-independent, counters the tendency of the simultaneously enhanced Ca2+ channel current to prolong the ventricular action potential. Using inside-out giant patches excised from guinea-pig myocytes, we show here that phosphorylation by the PKA catalytic subunit plus Mg-ATP elicits discrete Cl- channel currents. In almost symmetrical Cl- solutions (approximately 150 mM), unitary current amplitude scales with membrane potential, and reverses sign near 0 mV, to yield a single channel conductance of approximately 12 pS. Opening of the phosphorylated channels requires hydrolysable nucleoside triphosphate, indicating that phosphorylation by PKA is necessary, but not sufficient, for channel activation. The properties of these PKA-regulated cardiac Cl- channels are very similar, if not identical, to those of the cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial cell Cl- channel whose regulation is defective in patients with cystic fibrosis. The full cardiological impact of these Cl- channels and of their possible malfunction in patients with cystic fibrosis remains to be determined.     

代谢综合征左心功能研究进展

 简述了代谢综合征(metalbolic syndrome,MS)的定义及临床诊断标准,综述了高血压(EH)、肥胖、血糖异常、血脂异常等危险因素与左室心功能间的关系,分析了多种危险因素聚集一体的MS 的心功能变化特点。MS 患者的左室功能降低是由多个心血管危险因素引起,会导致多个复杂的代谢反应,影响心肌的结构和代谢环境,也改变了心肌功能和心肌能量。因此MS 患者在有症状的心力衰竭发展之前,可能存在一段时间亚临床的左心室功能障碍。