Effect of lidocaine on the electrophysiological properties of ventricular muscle and Purkinje fibers

Preparations of right ventricular papillary muscle and false tendon (Purkinje fiber) were obtained from dog hearts, placed in a bath perfused with Tyrode solution, and observed both under control conditions and during exposure to lidocaine in concentrations from 1 x 10(-7) to 5 x 10(-4) mole/liter. Transmembrane voltages were recorded from both ventricular muscle (VM) and Purkinje fibers (PF) of spontaneously beating and electrically driven preparations. Low concentrations (1 x 10(-6) and 1 x 10(-5) mole/liter) attenuated or abolished phase 4 (diastolic) depolarization and spontaneous firing in PF without decreasing their diastolic excitability. Concentrations of 1 x 10(-5) mole/liter produced maximal shortening of both action potential duration (APD) and effective refractory period (ERP) and made the ERP long relative to APD; the latter alteration was more prominent in VM. At concentrations /= 1 x 10(-4) mole/liter) did not cause further shortening of APD or ERP in either VM or PF but did produce a decrease in peak V(max) of phase 0 and membrane responsiveness. In most cases, these concentrations also caused a decrease in RP or DTMV(max) and action potential amplitude, with progression to bizarre action potential depolarization and inexcitability. These properties of lidocaine are strikingly different from those of quinidine or procaine amide. The mechanisms responsible for lidocaine's in vivo antiarrhythmic action are discussed.     

Pretreatment with pinacidil promotes arrhythmias in an isolated tissue model of cardiac ischemia and reperfusion

It is not clear whether activation of ATP-sensitive potassium channels (K(ATP)) with pinacidil in advance of ischemia and reperfusion promotes or suppresses arrhythmias. This study determines the effects of pinacidil pretreatment on arrhythmias and the changes in cellular electrophysiological parameters in segments of guinea pig right ventricular free walls exposed to simulated ischemia and reperfusion. Microelectrode recordings were made from endo- and epicardium during endocardial pacing. Preparations were superfused with Tyrode's solution and then exposed for 5 min to either 100 muM pinacidil or its solvent. After a 5-min washout, preparations were exposed to 15 min of ischemic conditions (hypoxia, hypercapnia, hyperkalemia, acidosis, lactate accumulation, and glucose-free) followed by reperfusion with Tyrode's solution. Pinacidil pretreatment increased ischemia-induced abbreviation of endo- and epicardial action potential durations and effective refractory periods. Pinacidil had no effect on endocardial conduction times but greatly prolonged transmural conduction during ischemia and early reperfusion, and it increased the incidence of transmural conduction block. Pinacidil pretreatment caused a significant increase in the incidence of arrhythmias in ischemia and reperfusion. Reperfusion arrhythmias in control preparations had electrophysiological characteristics of activity initiated by afterpotentials; however, arrhythmias with these characteristics were absent in pinacidil-pretreated preparations, and all reperfusion arrhythmias exhibited characteristics of reentry. The increased incidence of re-entrant arrhythmias is likely explained by pinacidil-induced reduction in effective refractory periods in combination with prolonged transmural conduction times. Thus, pinacidil pretreatment enhanced the effects of ischemia and reperfusion on action potential duration, effective refractory period, and transmural conduction, and it promoted re-entrant arrhythmias.     

Differential effects of glyburide on premature beats and ventricular tachycardia in an isolated tissue model of ischemia and reperfusion.

Possible anti- and proarrhythmic effects of glyburide, an ATP-sensitive K+ channel blocker, were assessed in an isolated tissue model of reperfusion. Transmembrane electrical activity was recorded from endo- and epicardium of isolated segments of guinea pig right ventricular free walls, or two sites on papillary muscles with microelectrodes. An electrocardiogram was recorded by two electrodes placed at opposite ends of the tissue bath. Regular stimulation was delivered to endocardium. Tissues were exposed to simulated ischemia for 15 min and then were reperfused with normal Tyrode's solution. Rapid sustained or nonsustained ventricular tachycardia, bigeminy or trigeminy with characteristics of transmural re-entry occurred early in reperfusion in 50% of free walls. Triggered arrhythmias with characteristics of oscillatory afterpotentials (delayed afterdepolarizations) occurred in 20%. Arrhythmias were accompanied by prolongation of transmural conduction times and abbreviation of endocardial effective refractory periods and action potential durations. Glyburide (3 or 30 microM) significantly attenuated abbreviation of action potential durations and effective refractory periods during ischemic conditions and early reperfusion. Neither endocardial nor transmural conduction times were modified by glyburide; however, glyburide significantly decreased the incidence of transmural conduction block during ischemic conditions. Glyburide abolished reperfusion arrhythmias with characteristics of re-entry, but potentiated oscillatory afterpotentials in papillary muscles and triggered arrhythmias with characteristics of oscillatory afterpotentials in free walls. Identical effects were seen with glyburide present in ischemic solution, or in both ischemic and reperfusion solutions, but no effect was observed with glyburide present only in reperfusion. Our study demonstrates possible cellular mechanisms underlying simultaneous pro- and antiarrhythmic drug effects exerted on late premature beats and rapid arrhythmias and closely coupled premature beats.     

Effects of lysophosphatidylcholine on electrophysiological properties and excitation-contraction coupling in isolated guinea pig ventricular myocytes.

Lysophosphoglyceride accumulation in ischemic myocardium has been implicated as a cause of arrhythmias. We examined the effects of lysophosphatidylcholine (LPC) in isolated guinea pig ventricular myocytes. In paced myocytes loaded with the Ca2+ indicator Indo-1-AM and studied at room temperature, 20 microM LPC caused an initial positive inotropic effect followed by spontaneous automaticity, a decline in active cell shortening, and progressive diastolic shortening (contracture) leading to cell death. These changes were accompanied by a progressive increase in cytosolic [Ca2+]i. In patch-clamped myocytes dialyzed internally with high EGTA concentrations, LPC caused membrane depolarization, shortening of the action potential duration, and abnormal automaticity as seen in multicellular preparations. Voltage clamp experiments revealed the appearance of a nonselective leak conductance without significant changes in the delayed rectifier K+ current, inward rectifier K+ current, L-type Ca2+ current, and T-type Ca2+ current. Pretreatment with 20 mM caffeine and [Ca2+]o-free solution did not prevent the leak current. In patch clamped myocytes loaded with 0.1 mM Fura-2 salt, the [Ca2+]i transient induced by either voltage clamps or brief caffeine exposure remained normal until the nonselective leak current developed. The Na(+)-Ca2+ exchange current elicited during caffeine-induced [Ca2+]i transients also did not appear to be altered by LPC. Qualitatively similar results were obtained in myocytes studied at 35 degrees C. The membrane detergent saponin (0.005% wt/wt) mimicked all of the effects of LPC. We conclude that under these experimental conditions the effects of LPC are most compatible with a detergent action causing membrane leakiness with resultant depolarization, [Ca2+]i overload, and contracture.     

缺血预适应对膨胀离体大鼠心室所致心律失常的影响

目的 观察缺血预适应对膨胀离体大鼠心室所致心律失常的影响。方法 采用Langendorff方法灌流离体大鼠心脏。将可充灌液体的乳胶球囊通过左心房及二尖瓣置于左心室,通过向乳胶球囊注射液体对左室进行膨胀,记录膨胀前和膨胀过程中左室心电图和左室压力、冠脉流量和心率;并计算对照组和各实验组由膨胀诱发心律失常的发生率和持续时间。结果 通过乳胶球囊膨胀左室,在左室舒张末压增加相同的情况下,缺血预适应组较对照组室性早搏和室性心动过速发生率均降低,持续时间显著缩短;加入维拉帕米、白屈菜赤碱或格列本脲后,室性早搏和室性心动过速发生率均增高,持续时间延长;单纯维拉帕米、白屈菜赤碱或格列本脲组心律失常发生情况和对照组相似。结论 对大鼠心室进行膨胀可诱发心律失常;缺血预适应对心律失常的发生具有抑制作用;细胞内钙离子浓度的短暂升高可能是缺血预适应发挥抑制作用的驱动因子;ATP敏感性钾通道及蛋白激酶c在缺血预适应过程中可能发挥了重要作用。     

κ-阿片受体激动剂U50488H对缺血/再灌注损伤大鼠冠状微循环和室性心律失常的影响

目的 探讨选择性κ-阿片受体激动剂U50488H对缺血/再灌注损伤大鼠冠状微循环和室性心律失常的影响,明确其对缺血/再灌注心肌是否有直接的保护作用.方法 32只大鼠按照随机原则分为四组,每组8只,分别为假手术组(A组)、缺血/再灌注(I/R)组(B组),U50488H I/R组(C组)和Nor-BNI(特异性阿片受体阻滞剂) U50488H I/R组(D组).实验组通过开胸结扎冠脉前降支制备大鼠缺血/再灌注模型,观察各组大鼠的心肌超微结构的改变和对室性心律失常的影响.结果 ①C组与B、D组比较,微血管显著扩张(P＜0.05);②C组与B、D组比较,室性心律失常的发生率明显下降.结论 U50488H可通过激活心脏κ-阿片改善缺血/再灌注大鼠的微循环、降低大鼠心肌缺血/再灌注室性心律失常的发生率,从而发挥心脏直接保护作用,该作用也可被选择性κ-阿片受体阻滞剂Nor-BNI所拮抗.     

Electrophysiological effects of amrinone and milrinone in an isolated canine cardiac tissue model of ischemia and reperfusion

The purpose of this study was to determine if amrinone or milrinone after the electrophysiological responses of canine ventricular tissues to "ischemia" or reperfusion. Isolated canine Purkinje tissue-papillary muscle preparations were studied using standard microelectrode techniques. Tissues were superfused for 10 min with a solution that mimicked ischemia (hypoxia, acidosis, elevated lactate levels and zero substrate). Reperfusion with normal Tyrode's solution was then instituted for 60 min. Next, tissues were equilibrated with amrinone (5.3 X 10(-4) M) or milrinone (2.5 X 10(-4) M) for 15 min and the protocol was repeated with drug in all solutions. Without drug, ischemic conditions resulted in moderate depolarization of Purkinje and muscle tissues. Reperfusion caused a rapid hyperpolarization in Purkinje tissue. This was followed by a phase of mild depolarization associated with enhanced pacemaker activity. All preparations recovered by 45 min of reperfusion. With amrinone or milrinone present, the changes in membrane potential induced by conditions of ischemia and reperfusion were not different from control. However, an early phase of very rapid ectopic activity was seen during reperfusion with amrinone or milrinone. This ectopic activity had a constant cycle length during the pauses in stimulation. However, irregular patterns of spontaneous and driven beats were observed when electrical stimulation was superimposed on the ectopic activity. Amrinone and milrinone also increased pacemaker activity in Purkinje tissue but this occurred later in reperfusion. This study demonstrates that amrinone and milrinone sensitize isolated canine ventricular tissues to the arrhythmogenic effects of reperfusion. The mechanism underlying the arrhythmic activity elicited by the bipyridines is not clear, but may involve re-entry or abnormal automaticity.     

利多卡因预处理对肾脏缺血再灌注大鼠心肌损伤的影响

目的:观察利多卡因对肾脏缺血再灌注大鼠心肌损伤的影响.方法:健康Wistar大鼠36只,体重300～350 g,随机分为3组(n=12),假手术组(sham组)只分离肾动脉不夹闭;肾缺血再灌注组(I/R组),双肾缺血60min、再灌注4 h;利多卡因组(L组)肾动脉阻断前静脉注射利多卡因5mg/kg,I/R组、sham组注射等量生理盐水,术中观察不同时间点的血压、心率.实验结束后处死大鼠,光镜观察心肌组织形态学改变,测定血浆心型脂肪酸结合蛋白(H-FABP)含量,心肌组织中性粒细胞弹性蛋白酶(NE)含量,肿瘤坏死因子-α(TNF-α)的表达.结果:光镜下可见I/R组呈明显心肌损伤的形态学变化,L组心肌组织损伤明显改善.I/R、L组血浆H-FABP,心肌组织NE、TNF-α较sham组升高,但是I/R组高于L组(P<0.05).结论:利多卡因预处理对肾脏缺血再灌注大鼠心肌损伤具有一定程度的保护作用,其机制可能与减轻肾缺血再灌注后心肌组织中性粒细胞浸润及下调TINF-α表达有关.     

I(Ks) blockade in border zone arrhythmias from guinea-pig ventricular myocardium submitted to simulated ischemia and reperfusion

I(Ks) blockade might be a promising way to treat tachyarrhythmia because of the accumulation of activated potassium channels. However, I(Ks) blockade during ischemia/reperfusion has not been investigated. Thus, the electrophysiological effects of two I(Ks) blockers, chromanol 293B (10 μm) and HMR 1556 (1 μm), were assessed in an in vitro model of border zone between normal and ischemic/reperfused right ventricular myocardium from guinea-pigs, and classic electrophysiological parameters and the incidence of arrhythmias were studied. HMR 1556 and chromanol 293B exhibited slight conventional class III effects on action potential duration in the normal zone (NZ) (APD(90) : -2 ± 5%, not significant (NS); +6 ± 3%, NS; and +5 ± 1%, P < 0.05, respectively, in control, HMR 1556, and chromanol 293B groups) but failed to oppose its decrease after 30 min of simulated ischemic superfusion (APD(90) : -52 ± 5%, P < 0.01; -64 ± 5%, P < 0.01; and -61 ± 3%, P < 0.01, respectively, in control, HMR 1556, and chromanol 293B groups), leading to repolarization dispersion between normal and ischemic zones. Chromanol 293B and HMR 1556 prolonged APD(90) during reperfusion, respectively, by +11 ± 1%, P < 0.01 and +25 ± 4%, P < 0.01 in the NZ and by +13 ± 3%, NS and +31 ± 2%, P < 0.01 in the simulated ischemic zone. Both compounds exhibited neutral arrhythmogenic effects during ischemia or reperfusion. Thus, I(Ks) blockade was neutral on the occurrence of ventricular arrhythmias during ischemia and reperfusion in guinea-pig ventricular tissue.     

Comparative pharmacodynamics of intravenous lidocaine in patients with acute and chronic ventricular arrhythmias.

OBJECTIVE: To evaluate the pharmacodynamics of intravenous lidocaine in patients with acute-onset and chronic ventricular arrhythmias. DESIGN: Open-label, pharmacodynamic evaluation. SETTING: Private, university-affiliated, hospital coronary-care unit. PATIENTS: Twenty cardiac patients with acute-onset ventricular ectopy and 20 with chronic ventricular ectopy. INTERVENTIONS: Intravenous lidocaine was administered to all patients as a 1-mg/kg bolus, a 0.5-mg/kg bolus, and a 2.8-mg/min constant infusion for 48 hours. MAIN OUTCOME MEASURES: Changes in ventricular premature beat (VPB) frequency against total treatment period frequency and by an hour-to-hour assessment of changes in VPB frequency compared with total baseline frequencies. Response was defined as greater than or equal to 80 percent total VPB reduction, greater than or equal to 90 percent paired VPB reduction, and total abolition of nonsustained ventricular tachycardia events. RESULTS: A statistically significant difference in the pharmacodynamic effects of lidocaine were observed during the first eight hours of treatment in patients with acute-onset and chronic VPBs. The number of patients with acute-onset VPBs who responded to lidocaine in the first hour of treatment did not change significantly over the remaining hours of treatment. Response to lidocaine was less in patients with chronic VPBs than in patients with acute-onset VPBs. The response rate to lidocaine was significantly less during the first eight hours in patients with chronic VPBs than in patients with acute-onset VPBs. Following eight hours of treatment, the response rates between acute-onset and chronic VPB patients were not significantly different. Mean lidocaine plasma concentrations were not different between the groups. In addition, there were no significant differences in the incidence of adverse effects between the two groups. CONCLUSIONS: The onset of antiarrhythmic effect as measured by suppression of ventricular ectopy is delayed in patients with chronic VPBs compared with patients with acute-onset VPBs. Decisions about lidocaine response in patients with chronic VPBs cannot be made accurately in the first eight hours of therapy.     

Ischemic postconditioning's benefit on reperfusion ventricular arrhythmias is maintained in the senescent heart

The purpose of this study is to determine if postconditioning's beneficial effect on ventricular arrhythmias is maintained in elderly hearts. In elderly populations, the cardioprotective effects of ischemic preconditioning are lost. Previously, the authors observed that ischemic postconditioning markedly reduced reperfusion-induced ventricular arrhythmias in adult rats. Whether this benefit is maintained in senescent hearts is unknown. Here, the authors study young adult rats compared with senescent animals. They chose 24-month-old Fischer female rats as these rats are approaching the end of their normal life span. Unlike some studies that suggest that the benefits of preconditioning and postconditioning are lost in the elderly, their data show that antiarrhythmic protection conferred by postconditioning is present in both the young and old rats.     

Effects of trapidil on intestinal mucosal barrier function and bacterial translocation after intestinal ischemia and reperfusion in an experimental rat model

Background: Intestinal ischemia and reperfusion may be the primary triggers of mucosal barrier impairment, cytokine expression, and bacterial translocation (BT). Trapidil is a phosphodiesterase and platelet-derived growth factor inhibitor that reduces lipid peroxidation and inhibits the production of cytokines.Objective: The goal of this study was to assess whether trapidil might protect the intestinal epithelial barrier by inhibiting lipid peroxidation and proinflammatory cytokines by testing the effect of trapidil on intestinal barrier function in an experimental ischemia/reperfusion (I/R) rat model.Methods: Trapidil was used in a rat model of intestinal barrier dysfunction caused by intestinal ischemia for 40 minutes followed by reperfusion for 12 hours. To do this, the rats were randomized to 1 of 4 treatment groups, as follows: (1) sham surgery and saline administration (1 mL IV) (Sham group); (2) sham surgery and trapidil administration (8 mg/kg IV) (Sham+T group); (3) I/R and saline administration (1 mL IV) (I/R group); and (4) I/R and trapidil administration (8 mg/kg IV) (I/R+T group). Intestinal barrier function was assessed by histopathologic examination, blood malondialdehyde (MDA) level, and BT.Results: The I/R+T group showed significantly less incidence of BT compared with the I/R group in the liver and reduced median colony count of translocated bacteria in mesenteric lymph nodes, liver, spleen, and peritoneum compared with the I/R group. Furthermore, the mean blood MDA level demonstrated that lipid peroxidation was significantly decreased in the I/R+T group compared with the I/R group. Histopathologic findings revealed that trapidil administration before reperfusion preserved intestinal mucosal integrity and inhibited the infiltration of inflammatory cells into the intestines.Conclusions: In this experimental study, a correlation seemed to exist between intestinal barrier dysfunction and BT. Intestinal barrier dysfunction may allow a large amount of bacteria to pass from the gut to distant organs. Trapidil treatment may inhibit BT by preserving intestinal barrier by inhibiting thromboxane A₂, lipid peroxidation, proinflammatory cytokines, and stimulated prostacyclin. Future dose- and time-dependent studies will be helpful in revealing the effects of trapidil on BT.     

川芎嗪在骨骼肌缺血再灌注损伤中的作用

目的:观察川芎嗪对兔缺血再灌注骨骼肌相关生化指标含量的影响以及超微结构的改变,探讨川芎嗪对骨骼肌缺血再灌注损伤的作用。方法:实验于2004-06/2004-08在潍坊医学院显微解剖学实验室完成。取清洁级成年新西兰白兔30只,建立后肢骨骼肌缺血再灌注损伤模型。实验随机分为对照组、缺血再灌注组和川芎嗪组,每组10只。缺血后4h,川芎嗪组自耳缘静脉注射盐酸川芎嗪注射液(含川芎嗪20g/L,山东潍坊制药厂有限公司生产,批号:030618)5mg/kg,对照组及缺血再灌注组注射等量生理盐水。注射完毕后立即撤去血管夹和橡皮带以恢复供血,再灌注后2h3组分别自术侧股静脉采集血样3mL,制备血清,测定天冬氨酸氨基转移酶、乳酸脱氢酶、肌酸激酶、丙二醛和超氧化物歧化酶含量;取术侧胫前肌,常规制备超薄切片,行电镜观察。结果:30只动物均进入结果分析。①缺血再灌注组血清天冬氨酸氨基转移酶、乳酸脱氢酶、肌酸激酶、丙二醛含量明显高于对照组[(142.2±8.1),(27.3±3.5)U/L;(318±35)(153±21)U/L;(3141±271),(1783±289)U/L;(5.86±0.59),(3.77±0.43)μmol/L;t=47.237～8.856,P<0.01],川芎嗪组与对照组比较除天冬氨酸氨基转移酶外均无明显升高[(59.7±3.3)U/L,t=13.320,P<0.01]。②缺血再灌注组超氧化物歧化酶活性明显低于对照组[(325.51±30.62),(443.49±38.13)NU/mL,t=8.404,P<0.01],川芎嗪组与对照组比较无明显降低[(422.37±23.77),(443.49±38.13)NU/mL,t=1.504,P>0.05]。③电镜下观察可见缺血再灌注组显示线粒体空泡样变,嵴断裂,毛细血管内皮细胞微绒毛减少,三联体异常,双侧终池宽大,横小管粗细不等;川芎嗪组三联体完整,糖原颗粒较多,毛细血管内皮细胞内有吞饮小泡,内皮细胞可见轻微损伤,肌纤维基本正常。结论:川芎嗪可减轻缺血再灌注对骨骼肌造成的损伤,对缺血再灌注骨骼肌具有保护作用。     

川芎嗪在骨骼肌缺血再灌注损伤中的作用

目的：观察川芎嗪对兔缺血再灌注骨骼肌相关生化指标含量的影响以及超微结构的改变，探讨川芎嗪对骨骼肌缺血再灌注损伤的作用。 方法：实验于2004-06／2004—08在潍坊医学院显微解剖学实验室完成。取清洁级成年新西兰白兔30只，建立后肢骨骼肌缺血再灌注损伤模型。实验随机分为对照组、缺血再灌注组和川芎嗪组，每组10只。缺血后4h，川芎嗪组自耳缘静脉注射盐酸川芎嗪注射液（含川芎嗪20g/L，山东潍坊制药厂有限公司生产，批号：030618）5mg／kg，对照组及缺血再灌注组注射等量生理盐水。注射完毕后立即撤去血管夹和橡皮带以恢复供血，再灌注后2h3组分别自术侧股静脉采集血样3mL，制备血清，测定天冬氨酸氮基转移酶、乳酸脱氢酶、肌酸激酶、丙二醛和超氧化物歧化酶含量；取术侧胫前肌，常规制备超薄切片，行电镜观察。 结果：30只动物均进入结果分析。①缺血再灌注组血清天冬氨酸氨基转移酶、乳酸脱氢酶、肌酸激酶、丙二醛含量明显高于对照组[（142．2&;#177;8．1）。（27．3&;#177;3．5）U／L；（318&;#177;35）（153&;#177;21）U／L；（3141&;#177;271），（1783&;#177;289）U／L；（5．86&;#177;0．59），（3．77&;#177;0．43）μmol／L；t=47．237-8．856，P〈0．01]，川芎嗪组与对照组比较除天冬氨酸氨基转移酶外均无明显升高[（59．7&;#177;3．3）U／L,t=13．320，P〈0．01]。②缺血再灌注组超氧化物歧化酶活性明显低于对照组[（325．51&;#177;30．62），（443．49&;#177;38．13）NU／mL,t=8．404，P〈0．01]，川芎嗪组与对照组比较无明显降低[（422．37&;#177;23．77），（443．49&;#177;38．13）NU／mL,t=1．504，P〉0．05]。③电镜下观察可见缺血再灌注组显示线粒体空泡样变，嵴断裂，毛细血管内皮细胞微绒毛减少，三联体异常，双侧终池宽大，横小管粗细不等；川芎嗪组三联体完整，糖原颗粒较多，毛细血管内皮细胞内有吞饮小泡，内皮细胞可见轻微损伤，肌纤维基本正常。 结论：川芎嗪可减轻缺血再灌注对骨骼肌造成的损伤，对缺血再灌注骨骼肌具有保护作用。     

Effects of Hypericum perforatum extract in a rat model of ischemia and reperfusion injury

Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants, and/or a depletion of antioxidants. A considerable body of recent evidence suggests that oxidative stress and exaggerated production of reactive oxygen species play a major role in several aspects ischemia and reperfusion. Hypericum perforatum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Because polyphenolic compounds have high antioxidant potential, in this study we evaluated the effect of H. perforatum extract on splanchnic artery occlusion (SAO) shock-mediated injury. SAO shock was induced in rats by clamping the superior mesenteric artery and the celiac trunk for 45 min. After 1 h of reperfusion, SAO-shocked rats developed a significant fall in mean arterial blood pressure. Treatment of rats with H. perforatum extract (applied at 25 mg/kg 15 min before reperfusion) significantly reduced a significant fall in mean arterial blood pressure and the migration of polymorphonuclear cells caused by SAO-shock. H. perforatum extract also attenuated the ileum injury (histology) as well as the increase in the tissue levels of myeloperoxidase and malondialdehyde caused by SAO shock in the ileum. Immunohistochemical analysis for nitrotyrosine and for poly ADP-ribosylated proteins revealed a positive staining in ileum from SAO-shocked rats. The degree of staining for nitrotyrosine and poly ADP-ribosylated proteins was markedly reduced in tissue sections obtained from SAO-shocked rats that had received H. perforatum extract. Reperfused ileum tissue sections from SAO-shocked rats showed positive staining for P-selectin and for intercellular adhesion molecule-1 in the vascular endothelial cells. H. perforatum extract treatment markedly reduced the intensity and degree of P-selectin and intercellular adhesion molecule-1 in tissue section from SAO-shocked rats. H. perforatum extract treatment significantly improved survival. In conclusion, this study demonstrates that H. perforatum extract exerts multiple protective effects in splanchnic artery occlusion-reperfusion shock and suggests that H. perforatum extract may be a candidate for consideration as a therapeutic intervention for ischemia-reperfusion injury.     

骨骼肌缺血再灌注损伤的机制

目的:对近年来骨骼肌缺血再灌注损伤的发病机制进行综述。资料来源:应用计算机检索MEDLINE、CBM、CNKI数据库及手工检索1998-01/2006-11期间的相关文献。中文检索词包括"骨骼肌,缺血再灌注损伤,发病机制";英文检索词有"Skeletal muscle","ischemia and reperfusion injury","oxygen freeradical","calcium overload"和"neutrophil"。资料选择:共收集到相关文献300篇,阅读全部文章的文题和大部分文章的摘要。选择文献所述内容与骨骼肌缺血再灌注损伤机制相关的文献。排除重复性研究。资料提炼:共得到符合纳入条件的文献55篇,排除145篇。选择其中30篇进行分析,英文24篇,中文6篇。资料综合:骨骼肌缺血再灌注损伤的机制由于有许多因素的介入而变的十分复杂,目前主要以氧自由基学说,钙超载学说和中性粒细胞学说为主,同时也注意到了一氧化氮和细胞凋亡以及微循环的无复流现象在其中的作用。结论:氧自由基学说,钙超载学说,中性粒细胞学说,一氧化氮,细胞凋亡以及微循环的无复流现象在骨骼肌缺血再灌注损伤中起着重要作用。     

Effects of dimethylpropranolol (UM-272) on the electrophysiological properties of guinea-pig ventricular muscles

The effects of dimethylpropranolol (UM-272) on transmembrane action potentials were examined in isolated right ventricular papillary muscles of the guinea pig. UM-272 (10(-5) to 3 X 10(-4) M) caused a dose-dependent decrease in the Vmax of the action potential. At 3 X 10(-4) M, a slight decrease in the amplitude of action potential was also observed. The resting potential and the action potential duration were not affected by the drug. In the presence of UM-272, trains of stimuli at rates higher than 0.1 Hz led to an exponential decline in Vmax (onset rate, 0.13-0.28 per action potential) to a new plateau level. This use-dependent block was augmented at the higher stimulation frequency. The time constant for the recovery of Vmax from the use-dependent block (offset) was 7.1 to 7.3 sec. In depolarized papillary muscles with 8 or 10 Mm [K+]0, the inhibitory action of UM-272 on Vmax of the first action potential after a long quiescent period (tonic block) was augmented markedly, but the rates of onset and offset of the use-dependent block were similar to those in normally polarized preparations under 5 mM [K+]0. The curves relating membrane potential and Vmax in preparations stimulated infrequently were shifted by 7.2 mV with UM-272 at 10(-4) M in the direction of more negative potentials. These findings suggest that UM-272 has kinetically similar use-dependent inhibitory action of the fast sodium channels of cardiac muscles as other Class Ia antiarrhythmic drugs like quinidine or procainamide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rotigaptide (ZP123) prevents spontaneous ventricular arrhythmias and reduces infarct size during myocardial ischemia/reperfusion injury in open-chest dogs

The antiarrhythmic and cardioprotective effect of increasing gap junction intercellular communication during ischemia/reperfusion injury has not been studied. The antiarrhythmic peptide rotigaptide (previously ZP123), which maintains gap junction intercellular communication, was tested in dogs subjected to a 60-min coronary artery occlusion and 4 h of reperfusion. Rotigaptide was administered i.v. 10 min before reperfusion as a bolus + i.v. infusion at doses of 1 ng/kg bolus + 10 ng/kg/h infusion (n = 6), 10 ng/kg bolus + 100 ng/kg/h infusion (n = 5), 100 ng/kg bolus + 1000 ng/kg/h infusion (n = 8), 1000 ng/kg bolus + 10 mug/kg/h infusion (n = 6), and vehicle control (n = 5). Premature ventricular complexes (PVCs) were quantified during reperfusion. A series of four or more consecutive PVCs was defined as ventricular tachycardia (VT). The total incidence of VT was reduced significantly with the two highest doses of rotigaptide (20.3 +/- 10.9 and 4.3 +/- 4.1 events; p < 0.05) compared with controls (48.7 +/- 6.0). Total PVCs were reduced significantly from 25.1 +/- 4.2% in control animals to 11.0 +/- 4.4 and 1.7 +/- 1.3% after the two highest doses of rotigaptide. Infarct size, expressed as a percentage of the left ventricle, was reduced significantly from 13.2 +/- 1.9 in controls to 7.1 +/- 1.0 (p < 0.05) at the highest dose of rotigaptide. Ultrastructural evaluation revealed no differences in myocardial injury in the infarct area, area at risk, border zone, or normal zone in vehicle and rotigaptide-treated animals. However, rotigaptide did increase the presence of gap junctions in the area at risk (p = 0.022, Fisher's exact test). Rotigaptide had no effect on heart rate, blood pressure, heart rate-corrected QT interval, or left ventricular end-diastolic pressure. In conclusion, these results demonstrate that rotigaptide is a potent antiarrhythmic compound with cardioprotective effects and desirable safety.