心肌片对缺血再灌注心肌细胞凋亡的影响

目的:观测心肌片对缺血再灌注心肌细胞凋亡的影响及可能机制。方法:H9c2细胞随机分为对照组、模型组、心肌片低中高剂量组,预给药24h后,建立心肌缺血/再灌注损伤(MI/RI)模型。检测细胞存活率,LDH释放水平,蛋白印迹法检测心肌细胞凋亡相关基因Bax,Bcl-2,Caspase-3,Cyt-C蛋白的表达以及AMPK磷酸化水平。结果:与模型组比较,心肌片提高细胞存活率,减少LDH水平,稳定线粒体膜电位,减少Bax,Caspase-3以及Cyt-C蛋白的表达,增加Bcl-2蛋白的表达,提高Bcl-2/Bax的比值(P<0.05)。进一步研究发现,这些保护作用被AMPK抑制剂Compound C取消。结论:心肌片能减轻心肌缺血再灌注损伤,抑制心肌细胞凋亡,其机制可能通过激活AMPK信号通路实现的。

抗心肌炎方配合西药分阶段治疗病毒性心肌炎37例

目的:观察抗心肌炎方配合西药分阶段治疗病毒性心肌炎的疗效。方法:采用中西医结合的方法分阶段治疗病毒性心肌炎37例,第一阶段(病毒复制期)用抗心肌炎方Ⅰ号;第二阶段(免疫损害期)抗心肌炎方Ⅱ号;第三阶段(恢复期)用心肌康片,配合常规西药治疗。并进行临床疗效观察。结果:总有效率100%。提示:运用中西医结合分阶段治疗病毒性心肌炎临床上有较好的疗效。

Applications of gene-chip for the detection of mutations in cTnI gene associated with FHCM

Mutations in cardiac troponin I （cTnI） gene were assessed based on gene-chip technology.Special probes were designed to fabricate the low-density gene-chip,which could detect the mutations in exons 3,5,7,and 8 of the cTnI gene simultaneously.For each exon,two oligonucleotide sequences labeled with fluorescein at the 5＇-end were designed,one （oligonucleotide Ⅰ） simulating the wild type and the other （oligonucleotide Ⅱ） simulating the mutant.Oligonucleotides Ⅰ and Ⅱ were mixed together to simulate the heterozygote.After optimizing the hybridization protocols,the fabricated gene-chip could detect the mutations in the exons of the cTnI gene with relative high sensitivity and specificity.The fully complementary probe gave a fluorescent signal almost 50% stronger than that of the one-base mismatched one,which is in accordance with the result from a theoretical estimate. An applicable special gene-chip is available to investigate and diagnose familial hypertrophic cardiomyopathy （FHCM） after further improvement.

Ion mechanism of isoproterenol on delayed afterdepolarization and triggered activity in the infarcted ventricle

Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infarcted rabbit model.Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk （healed myocardial infarction, HMI）. Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Iti and IC,_L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of I6 and calcium influxing

Cardiac Electrophysiological Differences Between Kunming and C57BL6/J Mice

Objective To investigate the alterations of cardiac electrophysiological properties and substantial mechanism and find the stable arrhythmia mouse model in Kunming （KM） and C57BL6/J （C57） mice. Methods Electrocardiogram recordings were used to analyze the QT interval in vivo, and mono- phasic action potential of right and left ventricular epicardium was recorded to elicit changes of action potential duration （APD） in conventional and programmed electrical stimulation （PES）. Transient outward potassium current （Its,） was recorded via whole-cell patch-clamp technique in single right and left epicardial myocytes. Results QT interval was prolonged in KM mice relative to C57 mice （62.51±4.47 ms vs. 52.59±4.85 ms, P〈0.05）. The APD at 50% repolarization of the left ventricular epicardium （18.60±0.91 ms vs. 12.90±0.35 ms）, and APDs at 50% （17.31±6.05 ms vs. 12.00±3.24 ms） and 70% repolarization （36.13±5.32 ms vs. 2 1.95±8.06 ms） of the right ventricular epicardium in KM mice were significantly pro- longed compared with C57 mice, respectively （all P〈0.05）. KM mice were more sensitive to PES-induced ventricular tachycardia （25%, 3 of 12 hearts）, and especially to Burst-induced ventricular tachycardia （50%, 6 of 12 hearts） compared with C57 mice, which were 20% （2 of 10 hearts） and 30% （3 of 10 hearts） respec- tively. It,, densities both in the left and right ventricular epicardial myocytes from KM mice were significantly decreased compared with C57 mice, respectively （all P〈0.01）. Conclusion Our data showed that KM mice with tile prolonged QT interval and APD are ruiner- abilities to ventricular arrhythmia, which are attributed to lower Ito densities in ventricular myocytes ob- tained from KM mice than that from C57 mice.

Effects of hypoxia on sodium current in rat cardiomyocytes

The aim of this study was to investigate the effect of hypoxia on the sodium current of rat cardiomyocytes in order to explore ion channel mechanism of cardiomyocyte hypoxia.The rat cardiomyocytes were isolated by acute enzymatic hydrolysis.A group of untreated cells were used to record sodium currents using whole-cell patch-clamp technique,another group was subjected to hypoxia and record sodium currents using same technique.The results showed that the morphological trajectory of sodium hypoxia was not changed compared with that of normal cells.The I-V curve of hypoxic cells was significantly higher than that of normal cells,and the peak current of INa was 15.68%higher than that of normal cells(P<0.0001).Activation potential of normal and hypoxia cells was about-40mV,the maximum peak current corresponds to the stimulation voltage of-25mV.The above results suggest that rat cardiomyocytes sodium current increases in the case of hypoxia.

L-type calcium current in right ventricular outflow tract myocytes of rabbit heart

The mechanism of idiopathic ventricular tachycardia originating from the right ventricular outflow tract （RVOT） is not clear. Many clinical reports have suggested a mechanism of triggered activity. However, there are few studies investigating this be- cause of the technical difficulties associated with examining this theory. The L-type calcium current （/Ca-L）, an important in- ward current of the action potential （AP）, plays an important role in arrhythmogenesis. The aim of this study was to explore differences in the APs of right ventricular （RV） and RVOT cardiomyocytes, and differences in electrophysiological character- istics of the ICa-L in these myocytes. Rabbit RVOT and RV myocytes were isolated and their AP and Ic,-L were investigated us- ing the patch-clamp technique. RVOT cardiomyocytes had a wider range of AP duration （APD） than RV cardiomyocytes, with some markedly prolonged APDs and markedly shortened APDs. The markedly shortened APDs in RVOT myocytes were abolished by treatment with 4-AP, an inhibitor of the transient outward potassium current, but the markedly prolonged APDs remained, with some myocytes with a long AP plateau not repolarizing to resting potential. In addition, early afterdepolariza- tion （EAD） and second plateau responses were seen in RVOT myocytes but not in RV myocytes. RVOT myocytes had a high- er current density for/Ca-L than RV myocytes （RVOT （13.16±0.87） pA pF-1, RV （8.59±1.97） pA pF-1; P〈0.05）. The ICa-L and the prolonged APD were reduced, and the EAD and second plateau response disappeared, after treatment with nifedipine （10 μmol L^-1）, which blocks the Ica-L. In conclusion, there was a wider range of APDs in RVOT myocytes than in RV myocytes, which is one of the basic factors involved in arrhythmogenesis. The higher current density for ICa-L is one of the factors causing prolongation of the APD in RVOT myocytes. The combination of EAD with prolonged APD may be one of the mechanisms of RVOT-VT generation.

Effect of electroacupuncture preconditioning at “Nèiguān” (内关 PC 6) on gene expression of myocardial opioid receptors in rats with ischemia-reperfusion

Objective To explore protective effects of electroacupuncture at ＂Nèiguān＂ （内关 PC 6） for preconditioning on myocardial ischemia-reperfusion injury （MIRI） and the mechanisms involved. Methods Forty-eight male Wistar rats were randomly divided into a sham operation group （Group N）, a MIRI group （Group M） and an electroacupuncture （EA） group （Group E）. The MIRI model was established by ligating the left anterior descending artery （LAD） for 30 min followed by reperfusion for 120 min. Partition sutures were passed under LAD without ligation for rats in Group N. Rats in Group E were pretreated with electroacupuncture （EA） applied at bilateral ＂Nèiguān＂ （内关 PC 6） for 20 min once a day for 3 consecutive days before ischemia. The infarct size plus the area at risk was evaluated by 2,3,5-triphenyltetrazolium chloride staining, and serum isoenzyme of creatine kinase （CK-MB） and lactate dehydrogenase （LDH） levels were measured by biochemical methods. Myocardium morphological changes were observed under light microscopy. The mRNA expressions of myocardial δ and κ opioid receptors （DOR and KOR） were tested by real-time RT-PCR measurements. Results The myocardial infarct size in Group E was more significantly decreased than that in Group M （P0.05）. The levels of CK-MB [（980？±？92） U/L] and LDH [（2743？±？124） U/L] in Group M were significantly higher than those in Group N [（312？±？41） U/L] and [（530？±？56） U/L], respectively （both P0.01）. The levels of CK-MB [（572？±？70） U/L] and LDH [（1819？±？97） U/L] in Group E were significantly lower than those in Group M （both P0.01）. There were no significant differences in mRNA expressions of DOR and KOR between Group M and Group N （both P0.05）, but DOR expression in Group E was significantly higher than that either in Group M or in Group N （both P0.01 ）. No significant differences were found in KOR expression among the three groups （all P0.05）. Conclusion Up-regulation of expression of δ opioid receptors may be involved in protective effects of EA at Nèiguān （内关 PC 6） for preconditioning on MIRI.

Early reperfusion strategy for acute myocardial infarction:a need for clinical implementation

Reperfusion is the key strategy in acute ST-segment elevation myocardial infarction (STEMI) care,and it is time-dependent.Shortening the time from symptom to reperfusion and choosing the optimal reperfusion strategy for STEMI patients are great challenges in practice.We need to improve upon the problems of low reperfusion rate,non-standardized treatment,and economic burden in STEMI care.This article briefly reviews the current status of reperfusion strategy in STEMI care,and also introduces what we will do to bridge the gap between the guidelines and implementation in the clinical setting through the upcoming China STEMI early reperfusion program.

Increased intracellular calcium concentration causes electrical turbulence in guinea pig ventricular myocytes

Dysregulation of intracellular Ca2+ homeostasis is associated with various pathological conditions and arrhythmogenesis of the heart.The objective of this study was to investigate the effects of an acute increase in intracellular Ca2+ concentration ([Ca2+] i) on the electrophysiology of ventricular myocytes by mimicking intracellular Ca 2+ overload.The [Ca2+] i was clamped to either a controlled (65-100 nmol L-1) or increased (1 μmol L-1) level.The transmembrane action potentials and ionic currents were recorded using whole-cell patch clamp techniques.We found that the acute increase in [Ca2+] i shortened the action potential duration,reduced the action potential amplitude,maximum depolarization velocity and resting membrane potential,caused delayed after-depolarizations (DADs),and triggered activity--compared with these parameters in the control.The increased [Ca2+] i augmented late I Na in a time-dependent manner,reduced ICaL and IK1,and increased IKr but not IKs.The results of this study can be used to explain calcium overload-induced ventricular arrhythmias.