AIM: To investigate the electrophysiological changes of diabetic myocardium and effects of cyclovirobuxine D (CVB-D) on its electrophysiology. METHODS: Diabetes was induced in male SD rats, using a single injection of alloxan into tail vein. Untreated age-matched animals were used as controls. Animal electrocardiogram (ECG) was recorded by 2 weeks. Effects of CVB-D on isolated right ventricular papillary muscle from experimental diabetic rats and control group were observed by recording the transmembrane potentials with conventional glass microelectrodes. RESULTS: QT intervals in ECG and action potential duration (APD) at all levels were significantly lengthened in myocardium from week 2 of diabetes. Within the concentration of 13.3-63.3 ?mol?L~(-1), CVB-D prologated APD of diabetes in dose-dependent manner and more than that of control. Within the concentration of 33.3-63.3 ?mol?L~(-1), CVB-D depressed RP, APA, V_(max) and OS of diabetes in dose-dependent way and more than that of control. In addition, CVB-D at concentration of 20 ?mol?L~(-1) prologated APD in a time-dependent manner. The most prologation of APD was attained about 40 min in control, while more than 40 min in diabetes. CONCLUSION: The results show that QT intervals in ECG and APD at all levels are significantly lengthened in myocardium from week 2 of diabetes. CVB-D prolongates APD and inhibits RP, APA, OS and V_(max) more in diabetes than in control.

AIM: To explore the probable mechanisms of diabetes-induced arrhythmias. METHODS: Diabetes was induced in male SD rats,using a single injection of alloxan into tail vein. Untreated age-matched animals were used as controls. All animals were observed by 2,4,6 and 8 weeks,respectively. Transmembrane potentials were recorded with conventional glass microelectrodes. RESULTS: Action potential duration(APD) at all level (APD10,APD20,APD30,APD50,APD70,APD90) was significantly lengthened in right ventricular papillary muscle from week 2 of diabetes. At week 8,APD was more lengthened at any level of repolarization than that at week 2. No differences were observed in the maximum rate of depolarization(V_ max ),overshoot(OS) and action potential amplitude(APA) as well as the resting membrane potential(RP) from the 2th to 8th week of diabetes. CONCLUSION: The results indicate that prolongation of APD may be prominently responsible for the increased incidence of cardiac re-entry-arrhythmias and sudden death,especially at late stages of diabetes.

AIM: To investigate the effect and possible mechanisms of interleukin-2 (IL-2) on the cell contractility in cardiomyocytes during hypoxia and reoxygenation.METHODS: Glucose-free Krebs-Henseleit (K-H) solution, gassed with 95% N 2 and 5% CO 2 for hypoxia, were used. The cell contractility were determined after 20 min of hypoxia and 30 min of reoxygenation by the video tracking system. The parameters of cell contractility included peak velocity of cell shortening (+d L /d t max), peak velocity of cell relengthening (-d L /d t max), contraction amplitude (dL) and end-diastolic cell length.RESULTS: It was shown that during hypoxia, the cell contraction was depressed. All the parameters were unable to return to the pre-hypoxia level during reoxygenation. Pretreatment with IL-2 at 2?10 3 U/L attenuated the inhibitory effect of hypoxia/reoxygenation on contractility in single ventricular myocytes. The effect of IL-2 was reduced in the presence of 10 -8 mol/L nor-binaltorphimine (nor-BNI), a selective ?-opioid receptor antagonist. On blockade of protein kinase C with 3?10 -6 mol/L chelerythrine, the effect of IL-2 was significantly attenuated. The effect of IL-2 was also blocked by 10 -4 mol/L 5-hydroxydecanoate (5-HD), a mitochondrial ATP-sensitive potassium (K ATP ) channel blocker. CONCLUSIONS: The results of the present study provide evidence that pretreatment with IL-2 at 2?10 3 U/L attenuates the effect of hypoxia/reoxygenation on cell contraction in the isolated ventricular myocytes. The ?-opioid receptor mediates the effect of IL-2, in which activation of PKC and opening of mitochondrial ATP-sensitive potassium (mito K ATP ) channel are involved.

Objective To investigate the effectiveness and safety of transcatheter radiofrequency ablation guided by a three-dimensional mapping system (Ensite or Carto) for the treatment of complex cardiac arrhythmias. Methods A cohort of 123 consecutive hospitalized inpatients during the period from February 2006 to December 2008 were selected for this study. These patients suffered from various arrhythmias, including paroxysmal atrial fibrillation (n=58). Persistent or permanent atrial fibrillation (n=10), atrial flutter (n=13), atrial tachycardia (n=12) and ventricular tachycardia or frequent ventricular premature beats (n=30). Transcatheter radiofrequency ablation for arrhythmias was performed under the guidance of an EnSite3 000/NavX or Array mapping system in 80 cases, and under the guidance of a CARTO mapping system in the remaining 43 cases. Results Successful ablation of arrhythmias was obtained by single operation in 106 cases(86.18%). Including 59 cases with atrial fibriUation,11 cases with atrial flutter, 10 cases with atrial tachycardia, and 26 cases with ventricular tachycardia or premature ventricular beat. Ablation procedure was carried out and was successful in 10 cases with a successful rate of 94.31%, including 5 cases with atrial fibrillation. 1 case with recurred atrial flutter, 1 case with recurrent atrial tachycardia, and 3 cases with ventricular tachycardia or premature ventricular beat. After operation, complications occurred in 6 cases, including cardiac tamponade in 4 cases, distal embolism of the left anterior descending coronary artery in 1 case, and pulmonary embolism in 1 case. Conclusion Three-dimensional mapping system can clearly and stereoscopically display the cardiac structures. Therefore, this technique is of great value in guiding the transcatheter radiofrequency ablation for complex arrhythmias, in improving the success rate of ablation and in increasing the safety of the procedure.