普鲁卡因对离体豚鼠右心室缺血再灌注心肌电活动的影响

目的　研究普鲁卡因对离体豚鼠心室肌心律失常及跨壁传导等电生理特性的影响。方法　模拟在体正常和缺血再灌注条件,用玻璃微电极同时记录离体豚鼠心室肌内、外膜下心肌细胞跨膜电位。结果　普鲁卡因可明显地降低心律失常发生率、增加缺血再灌过程的心内膜传导时间和跨壁传导时间、延长心肌动作电位时程和有效不应期,并可使心肌兴奋性降低。结论　降低心肌兴奋性、消除折返激动和触发活动可能是普鲁卡因拮抗缺血再灌注心律失常的重要途径     

参麦注射液对正常及缺血再灌注离体豚鼠心脏的影响

目的观察参麦注射液(SM)对正常及缺血再灌注离体豚鼠心脏的影响。方法采用正常Langendorff灌流及缺血再灌注离体豚鼠心脏模型,观察SM对冠脉流量的影响,测定冠脉流出液中乳酸脱氢酶(LDH)活性及心肌组织丙二醛(MDA)、超氧化物歧化酶(SOD)的活性。结果SM可显著提高正常及缺血-再灌注离体豚鼠心脏的冠脉流量,减少缺血-再灌注后LDH的漏出总量,降低缺血再灌后心肌组织MDA的含量,升高SOD的活性。结论SM可增加正常及缺血-再灌离体豚鼠心脏冠脉流量,减轻缺血-再灌引起的心肌损伤。     

四氢巴马汀抗缺血再灌注心律失常的作用及其机理

四氢巴马汀(THP)5～15mg·kg~(-1)iv明显降低大鼠心肌缺血再灌注心律失常的发生率和心肌脂质过氧化物的含量。THP1、3和10μmol·L~(-1)使大鼠离体心室肌去氧肾上腺素量效曲线非平行性右移.最大反应压低,表现为非竞争性拮抗作用。THP10μmol·L~(-1)能显著抑制缺氧再给氧所致豚鼠离体心室肌的迟后除极和触发活动。表明THP有良好的抗缺血再灌注心律失常的作用.其机理是阻止氧自由基的损害作用和迟后除极的产生.而与心肌α_1受体可能无关。     

7-氯苄基四氢巴马汀对离体大鼠心肌缺血再灌损伤的保护作用

目的：研究７－氯苄基四氢巴马汀对离体大鼠心肌缺血再灌损伤的影响。方法：利用Ｌａｎｇｅｎｄｏｒｆ大鼠心脏，结扎冠状动脉前降支（ＬＡＤ），缺血１０ｍｉｎ后，再灌注２０ｍｉｎ，造成缺血再灌损伤模型。结果：７－氯苄基四氢巴马汀（７－ｃｈｌｏｒＢＴＨＰ）可明显减慢心率，消除再灌注引起的心室纤颤，明显缩短心律失常持续时间，并能抑制离体大鼠心肌缺血、复灌时磷酸肌酸激酶（ＣＰＫ）及乳酸脱氢酶（ＬＤＨ）释放增加。结论：７－ｃｈｌｏｒＢＴＨＰ具有抗离体大鼠再灌注心律失常作用，对缺血再灌注损伤心肌有保护作用，其作用机制可能与其减慢心率，减少缺血复灌时心肌酶释放有关。     

普罗帕酮和普鲁卡因胺抗犬缺血性快速室性心律失常的对比研究(英文)

目的　观察普罗帕酮对犬在体心脏缺血性快速室性心律失常的心电生理影响并与普鲁卡因胺对比 ,以探讨其抗缺血性快速室性心律失常的效果及作用机制。方法　用冠状动脉左前降支结扎并部分再灌注法造成犬急性前壁心肌梗死 ,5～ 8d后 ,辅以心室程控电刺激 (PES)技术及冠状动脉内恒定微量直流电刺激技术 ,并诱发与终止持续性室性心动过速和心室纤颤 ,制备成犬急性心肌缺血再灌注后可控性快速室性心律失常的在体心脏心电模型 ,心电图对比观察普罗帕酮及普鲁卡因胺的抗心律失常作用。结果　普罗帕酮及普鲁卡因胺均能显著地延长心肌梗死犬的心电图QTc间期 (P <0 .0 1 )及正常和缺血心肌的有效不应期 (P <0 .0 1 ) ,降低缺血心肌和左室心肌的有效不应期离散度 (P <0 .0 1 ) ,提高正常心肌和缺血心肌的舒张期兴奋阈值 (P <0 .0 1 ) ,抑制PES诱发的持续性室性心动过速和心室纤颤 (P <0 .0 1 ) ,并能预防犬急性心肌梗死后再次缺血所致的自发性室性心动过速和心室纤颤 (P <0 .0 5)。结论　①该犬在体心脏心电药理学实验模型具有较好的重复性、可靠性及临床相关性 ,是一种有价值的心电药理学实验研究模型。②普罗帕酮及普鲁卡因胺均具有抗缺血性快速室性心律失常的心电生理作用 ,是有效的抗颤药物 ,两药效果相似     

牛磺酸对豚鼠心脏实验性“缺血”和再灌注时心肌电生理的影响

用离体豚鼠心室乳头肌的细胞电生理实验观察牛磺酸在心肌模拟缺血和再灌注状态下的电生理保护作用。结果表明１０￣２０ｍｍｏｌ牛磺酸对正常灌注时的心肌跨膜电位无明显影响；“缺血”１０ｍｉｎ恢复对各组的ＡＰＤ均缩短，但至“缺血”３０ｍｉｎ时２０ｍｍｏｌ牛磺酸组ＡＰＤ完全恢复；再灌注５ｍｉｎ时１０￣２０ｍｍｏｌ牛磺酸使ＲＰ分别恢复至（９５．６８±７．５３２）％、（９４．４３±２．８）％，２０ｍｍｏｌ牛磺酸使Ａ     

银杏内酯对血小板活化因子加重离体豚鼠心肌缺血再灌注损伤的影响

目的:研究银杏内酯对外源性血小板活化因子(PAF)加重离体豚鼠心肌缺血再灌注损伤的影响.方法:采用离体豚鼠心脏Langendorff灌流装置,观察银杏内酯(4,8,16mg·L -1 )对离体豚鼠心肌再灌注心律失常、心肌组织丙二醛(MDA)、谷胱甘肽过氧化物酶(GSH-PX)、三磷酸腺苷酸酶(ATPase)以及冠脉流量(CF)的影响.结果:银杏内酯、普萘洛尔有效减少损伤心肌MDA含量及Ca 2 -ATP酶活力,增加GSH-PX活力,并且对抗PAF加重的离体豚鼠心肌缺血再灌注心律失常的发生.结论:银杏内酯对抗PAF加重离体豚鼠心肌缺血再灌注损伤的作用与拮抗PAF受体、抑制自由基产生、减少心肌细胞钙超载、防止心律失常的发生有关.     

2″-o-没食子酰基金丝桃苷对豚鼠右心室缺氧再给氧心肌电活动的影响

2″ ｏ 没食子酰基金丝桃苷 (ＰＣＡ 4 )是从鹿衔草 (ＰｙｒｏｌａＣａｌｌｉａｎｔｈａＨ Ａｎｄｒｅｓ)中分离出的单体成分 ,对在体大鼠心肌缺血再灌注损伤有明显的保护作用[1] 。本文利用豚鼠右心室游离壁缺氧再给氧心律失常 (ＩＲＡ)模型[2 ,3 ] ,研究ＰＣＡ 4对ＩＲＡ发生率以及心室肌跨膜电位和跨壁传导等电生理特性的影响。1　材料与方法1.1　药品与材料　ＰＣＡ 4 (含量 >99% )由西安交通大学药学院王军宪副教授分离提取。正常和缺氧Ｔｙｒｏｄｅｓ液的配制以及实验所用仪器、试剂均与文献相同[3 ,4] 。健康成年豚鼠 ,♀♂不限 ,体…     

触发活性在实验性心肌“缺血”和再灌注心律失常中的作用

离体豚鼠心室肌模拟“缺血”和再灌注的细胞电生理实验表明:(1)迟后除极电位(DAD)在心肌“缺血”时的发生率仅为16.7%,再灌注时增加到50%。如“缺血”台氏液中加入异丙肾素或增加钙含量,对缺血时的DAD 发生率无影响,再灌注时则分别增加到72.3%和57.1%,并见DAD 引发的持续触发活性;(2)早后除极电位(EAD)在心肌“缺血”时的发生率为8.3%,再灌注时为16.7%,且不受“缺血”台氏液中异丙肾素或高钙的影响,均未引发触发活性。     

IHC－66对离体豚鼠心房肌的影响

ＩＨＣ－６６（３０μｍｏｌ·Ｌ－１）对离体豚鼠心房肌能明显抑制收缩性，肾上腺素诱发的自律性，延长功能不应期，降低兴奋性；可明显抑制其正阶梯现象，降低右心房自发性搏动频率。结果表明，ＩＨＣ－６６的抗心律失常作用可能与其抑制Ｃａ２＋、Ｎａ＋的跨膜转运有关。     

Ventricular tachycardia in an isolated guinea pig ventricular free wall model of ischemia and reperfusion.

Electrical activity from endo- and epicardium was recorded from isolated segments of right ventricular free walls of guinea pigs using standard differential microelectrode techniques and a high-gain electrocardiogram (ECG). Stimulation was applied to the endocardium. Tissues were exposed to ischemic conditions for 10 min and then were reperfused with "normal" Tyrode's solution. Early premature beats or rapid ventricular tachycardia (VT) occurred in 36% of hearts during "ischemia" and 79% of hearts on reperfusion. Endocardial activation was not significantly slowed by ischemic conditions or reperfusion. However, transmural conduction times increased, and muscle action potential durations decreased during ischemic conditions and early reperfusion. Rapid VT began with alternating activation of endo- and epicardium, and continuous low-voltage ECG activity bridging diastole. Activation of epicardium was essential for occurrence of early premature beats and rapid VT. Hyperkalemia during ischemia promoted arrhythmias during "ischemia," but not during reperfusion. Oscillatory afterpotentials (OAP) also occurred during reperfusion (36%), but not during "ischemia". Our study provides an isolated tissue model that reproducibly generates tachycardias, and that permits study of ischemia and reperfusion-induced transmembrane activity and defects in transmural conduction.     

Effects of quinidine on arrhythmias and conduction in an isolated tissue model of ischemia and reperfusion.

Transmembrane electrical activity from endo- and epicardium and a high-gain ECG were recorded from isolated segments of guinea pig right ventricles. Endocardium was stimulated. Tissues were exposed to ischemic conditions for 15 min and then reperfused with "normal" Tyrode's solution. Ventricular tachycardia, bigeminy, or trigeminy with characteristics of transmural reentry occurred in early reperfusion in 68% of control hearts. Arrhythmias were associated with prolongation of the transmural conduction time (CT) and abbreviation of the endocardial effective refractory period (EP). Quinidine significantly suppressed reperfusion arrhythmias at 1 and 5 microM, slightly increased the incidence of arrhythmias at 10 microM, and again suppressed arrhythmias at 50 and 100 microM. At 1 and 5 microM, quinidine prevented or attenuated prolongation of the transmural CT by ischemic conditions and reperfusion. The transmural CT was not significantly changed at 10 microM, and was further prolonged at 50 and 100 microM quinidine. The endocardial ERP was prolonged by 50 and 100 microM quinidine during ischemic conditions and reperfusion. In epicardial slices, 5 microM quinidine shortened the CT transverse to the fiber orientation during reperfusion but had no effect on the longitudinal CT. Thus, antiarrhythmic efficacy of low concentrations of quinidine may occur through differential effects dependent on tissue anisotropy.     

Protective effects of D,L-carnitine against arrhythmias induced by lysophosphatidylcholine or reperfusion

Electrophysiological effects of lysophosphatidylcholine (50 or 100 microM) and D,L-carnitine (100 microM) were studied under control conditions and in response to simulated ischaemia and reperfusion using the superfused right ventricular free wall preparation from the guinea pig heart. Lysophosphatidylcholine, 100 microM, induced a significant depolarization of the maximum diastolic potential (MDP) in the epicardium, as well as the development of ventricular premature beats, salvos and ventricular tachycardia. Both coupled beats and abnormal automaticity were observed in lysophosphatidylcholine (100 microM)-treated preparations. Carnitine (100 microM) alone had no effect on preparations superfused with normal Tyrode solution. However, it delayed the time to onset and reduced the cumulative duration of lysophosphatidylcholine-induced arrhythmias (P less than 0.05). The incidence of lysophosphatidylcholine-induced abnormal automaticity and salvos was also significantly decreased in the presence of carnitine. Twenty minutes of simulated ischaemia caused depolarization of MDP as well as prolongation followed by block of transmural conduction. Lysophosphatidylcholine (100 microM) did not alter this response however, carnitine significantly reduced ischaemia-induced depolarization in the epicardium. All control preparations developed arrhythmic activity during 30 min of reperfusion. Carnitine accelerated recovery of MDP in the epicardium upon reperfusion, prolonged the time to onset of arrhythmic activity and reduced both its cumulative duration and incidence. In contrast, reperfusion in the presence of lysophosphatidylcholine (100 microM) significantly increased the incidence of arrhythmic activity. Carnitine exerted only minimal antiarrhythmic action when preparations were exposed to reperfusion in the presence of lysophosphatidylcholine. In conclusion, this study demonstrates that carnitine can modify various cellular mechanisms of arrhythmia induced by lysophosphatidylcholine or by reperfusion but is much less effective when lysophosphatidylcholine and reperfusion are combined.     

Protective effects of phosphatidylcholine against mechanisms of ischemia and reperfusion-induced arrhythmias in isolated guinea pig ventricular tissues

Summary The effects of exogenous phosphatidylcholine (PC) on some potential mechanisms of ischemia and reperfusion-induced arrhythmias were tested using the superfused right ventricular free wall of the guinea pig. Exposure of the preparation to simulated ischemia (hypoxia, acidosis, glucose deprivation and hyperkalemia) resulted in several electrophysiological derangements, including a marked depolarization of the maximum diastolic potential (MDP) in both endocardium and epicardium, shortening of the action potential duration (APD), and prolongation of the transmural conduction time followed by transmural conduction block. In a few preparations, coupled beats were also observed. Reperfusion was associated with arrhythmic activity in all preparations. Both the characteristics and the severity of reperfusion-associated arrhythmias were dependent upon the duration of the preceding ischemia. In hearts exposed to ischemic conditions for 40 min, transmural conduction block persisted until 45 min of reperfusion and no electrical activity was present in the epicardium during this time. However, both coupled beats as well as abnormal automaticity were observed in the endocardium. When the period of ischemia was reduced to 20 min, recovery from transmural conduction block occurred sooner and coupled beats and abnormal automaticity were detected in both epicardial and endocardial layers. Superfusion with PC during both ischemia and reperfusion (PC1 group), or during reperfusion only (PC2 group), significantly altered the response of the preparations to reperfusion. Following 40 min ischemia, preparations treated with PC recovered from transmural conduction block more rapidly (PC1 group, 4 min, P < 0.05; PC2 group, 23 min, ns), compared to control. In addition, both PC treated groups exhibited improved recovery of MDP in the epicardium early in reperfusion. Neither PC treatment altered the incidence of coupled beats but reperfusion-associated abnormal automaticity was abolished in both groups. In preparations exposed to 20 min of ischemia, PC reduced the duration of coupled beats from 5 ± 2 min in the control to 1 ± 0 min in both PC treated groups (P < 0.05). In addition, PC treatment decreased the incidence of abnormal automaticity from 7/10 in control preparations to 1/10 in both treated groups (P < 0.05). Severe ventricular tachycardia was observed in 3/10 control preparations, whereas it was completely absent in the PC treated groups. The present study demonstrates that exogenous PC can antagonize three important cellular mechanisms which may underlie reperfusion arrhythmias: transmural conduction block, coupled beats and abnormal automaticity.Abbreviations APD action potential duration - MDP maximum diastolic potential - PC phosphatidylcholine - PC1 PC included during both ischemia and reperfusion - P2 PC included during reperfusion only Send offprint requests to M. P. Moffat at the above address     

Potential cellular mechanisms of hydrogen peroxide-induced cardiac arrhythmias.

The electrophysiologic effects of hydrogen peroxide on the isolated guinea pig right ventricular free wall were studied using simultaneous recordings of action potentials from the epicardium and the endocardium. Exposure to hydrogen peroxide caused a time- and concentration-dependent change in action potential characteristics. Action potential durations at 50 and 90% of repolarization (APD50 and APD90, respectively) were significantly prolonged by hydrogen peroxide in both the epicardium and the endocardium. Although prolongation occurred at lower concentrations (0.5 mM) in the epicardium, increases in APD in response to higher concentrations of hydrogen peroxide (1 or 4 mM) were maintained for a longer period of time in the endocardium. In addition, hydrogen peroxide (1 or 4 mM) caused significant depolarization in the epicardium after 10 min, although this effect was observed only in the endocardium exposed to 4 mM hydrogen peroxide. Ventricular arrhythmias were observed in 5 of 7, 6 of 7, and 7 of 7 preparations exposed to 0.5, 1, and 4 mM hydrogen peroxide, respectively. The most frequently observed electrophysiologic abnormalities were associated with increased automaticity. Coupled beats, including clearly identifiable early and delayed depolarizations, were also observed. Verapamil (2 microM) and amiloride (0.1 mM) reduced both the incidence and the duration of hydrogen peroxide-induced arrhythmias but did not influence the effects on APD. This study is the first demonstration of hydrogen peroxide-mediated transmural dispersion in APD that could play an important role in the development of ventricular arrhythmias. In addition, our results demonstrate that hydrogen peroxide can induce ventricular arrhythmias through several cellular mechanisms, including increased automaticity, coupled beats, and triggered activity.     

腺苷对模拟缺血再灌注豚鼠心室肌细胞动作电位的影响及其离子机制

目的　研究腺苷 (Ado)在模拟缺血缺氧时对豚鼠心室肌细胞动作电位 (AP)、L 型钙电流 (ICa.L)和ATP敏感性钾电流 (IK .ATP)的影响。方法　在离体豚鼠心室肌和酶解法分离的单个豚鼠心室肌细胞上 ,分别应用细胞内微电极和全细胞膜片钳技术记录动作电位和电流。结果　在模拟缺血缺氧状态下 ,Ado剂量依赖性的增大动作电位时程 (APD)的缩短 (P <0 0 5 ) ;抑制再灌注后APD恢复 ,而表现出迟后恢复。在缺血缺氧状态下 ,ICa.L受到抑制 ,Ado并不加重心肌细胞缺血缺氧时ICa.L的减小 ,而再灌注后ICa .L的恢复比较缓慢 ,但同对照组比较无差异。Ado可加速缺血缺氧时IK .ATP的激活 ,Ado(10 0 μmol·L-1)组在缺血缺氧时和再灌注后IK .ATP较对照组均明显增大。结论　在缺血缺氧状态下 ,Ado可增大APD的缩短 ,抑制再灌注后APD的恢复 ,其机制主要在于在缺血缺氧状态下Ado增大了IK .ATP。     

Effects of angiotensin II type 1 receptor antagonist (candesartan) in preventing fatal ventricular arrhythmias in dogs during acute myocardial ischemia and reperfusion

Fatal arrhythmias may be prevented by long-term oral administration of angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 (AT 1 ) receptor antagonists. However, there have been no studies evaluating the electrophysiologic changes that occur with the acute administration of AT 1 receptor antagonists during acute myocardial ischemia and reperfusion. This study aimed to evaluate the ability of candesartan to prevent fatal arrhythmias during acute myocardial ischemia and reperfusion. The left anterior descending (LAD) coronary artery was ligated for 10 min and then reperfused for 10 min in 45 adult mongrel dogs. Candesartan (1 mg/kg) or saline was administered intravenously 10 min before ligation of the LAD coronary artery (candesartan group [n = 20] and control group [n = 25], respectively). Changes in ventricular effective refractory period (ERP) and intramyocardial conduction time (ICT) in the risk area were compared during LAD occlusion and reperfusion. Ischemia-induced shortening of ERP was inhibited in the candesartan group compared with the control. There was a 4.7 +/- 5.8% increase in ERP in the candesartan group, compared with a 11.5 +/- 6.3% shortening in the control group (p < 0.01). Prolongation of ICT was inhibited in the candesartan group compared with the control group during both ischemia and reperfusion (maximal prolongation of ICT: 0.1 +/- 3.0% vs. 37.7 +/- 9.6%, respectively; p < 0.01). Incidence of ventricular fibrillation was lower in the candesartan group than in the control group (25% [5/20] vs. 72% [18/25], respectively; p < 0.01). Candesartan suppresses changes in ERP and ICT during acute myocardial ischemia and reperfusion, suggesting that candesartan can prevent the development of fatal arrhythmias.     

千金藤立定碱的抗实验性心律失常作用

静脉注射 SPD10mg/kg,可增加豚鼠对哇巴因的耐受量;能预防急性心肌缺血诱发的大鼠及氯仿-肾上腺素引起的兔心律失常。腹腔注射SPD60mg/kg,可预防氯仿诱发的小鼠室颤。离体实验,发现SPD能抑制豚鼠乳头肌的收缩性,延长功能不应期,降低自律性,而对其兴奋性则无明显影响。     

Mibefradil is more effective than verapamil for restoring post-ischemic function of isolated hearts of guinea pigs with acute renal failure

The deleterious intracellular Ca(2+) overload in the ischemic-reperfusion injury of the heart can be even more expressed in subjects with acute renal failure in whom maintenance of intracellular Ca(2+) has already been disturbed in normoxia. To study the influence of acute renal failure in ischemic-reperfusion injury on the heart, we used isolated Langendorff's hearts of guinea pigs with gentamicin-induced acute renal failure. We examined arrhythmias, heart contractility and myocardial cell damage during reperfusion. Two specific Ca(2+) channel antagonists, mibefradil (0.1 and 1 microM) and verapamil (0.1 microM), were used to test the possible involvement of T-type and L-type Ca(2+) channels in these processes. We exposed hearts to 50 min of zero-flow global ischemia and 60 min of reperfusion. During reperfusion, unrecoverable ventricular fibrillation appeared more often in hearts of animals with acute renal failure than in control hearts (80% vs. 0%, respectively). Mibefradil, but not verapamil, applied either pre- or post-ischemically, terminated ventricular fibrillation in all hearts of animals with acute renal failure. Mibefradil (0.1 microM only) improved contractility in hearts of animals with acute renal failure during reperfusion by 30%. During reperfusion, lactate dehydrogenase (LDH) release rate increased less in hearts of guinea pigs with acute renal failure than in control hearts and only verapamil decreased it additionally. Thus, our results suggest a more important role of T- than of L-type Ca(2+) channels in ischemic-reperfusion injury in isolated guinea pig hearts with acute renal failure.