2-甲硫基三磷酸腺苷对心力衰竭兔心室电生理的影响

Effect of 2-methylthio-adenosine-5'-triphosphate on electrophysiological properties induced by congestive heart failure in rabbit

目的观察2-甲硫基三磷酸腺苷(2-MeS ATP)对充血性心力衰竭(CHF)心室电生理的影响。方法 45只雄性新西兰大耳白兔分为对照组、CHF组和2-MeS ATP组。CHF组和2-MeS ATP组均行CHF模型制备。CHF模型制备是经兔耳缘静脉注射异丙肾上腺素(每天每公斤体重0.3 mg,连续注射3周)诱导。喂养6个月后。记录在体心脏左心室单相动作电位(MAP)和程控以及短阵快速刺激方法观察静息膜电位(RMP)、动作电位幅度(APA)、最大上升速率(V_(max))、复极化到20%和50%以及90%时程(APD_(20)、APD_(50)、APD_(90))以及有效不应期(ERP)和室性心律失常诱发率等指标。2-MeS ATP组于CHF免静脉滴注2-MeS ATP(10 mg/kg)20 min,然后维持静脉滴注过程中完成上述指标检测。酶解法分离各组单个心室肌细胞全细胞膜片钳技术记录心室肌细胞瞬时外向钾电流(I_(to)),以各自指令电位为横坐标,相对应的电流密度为纵坐标,绘制电流-电压(I-V)曲线。2-MeS ATP组分离单个心室肌细胞后用含有2-MeS ATP(25μmol/L)的细胞外液灌流CHF心室肌细胞10 min完成上述试验。结果最后各组均入选10只兔。与对照组比较,CHF组RMP和APA明显降低,V_(max)减慢,APD均显著延长(P均<0.05);与CHF组比较,2-MeS ATP组RMP和APA增加,V_(max)增快,各APD都显著缩短(P均<0.05)。CHF组较对照组ERP显著延长,与APD_(90)的比值严重降低,诱发室性心律失常的刺激周长(BCL)明显增加,室性心律失常的诱发率上升,持续时间更长(P均<0.01);而2-MeS ATP组较CHF组ERP明显缩短,和APD_(90)的比值显著增加,被诱发室性心律失常的BCL严重缩短,室性心律失常的诱发率和持续时间均降低(P均<0.01)。与CHF组比较,2-MeS ATP组I_(to)的电流密度增加,当钳制电位为+50 mV时,2-MeS ATP能够使I_(to)的电流密度由CHF组的(7.94±3.53)pA/pF增加到(11.79±4.51)pA/pF(P<0.01),2-MeS ATP组较CHF组心室肌细胞I_(to)的I-V曲线明显上抬,接近对照组。结论 2-MeSATP可以使CHF心肌APD缩短,室性心律失常的易感性降低,起到抗CHF后室性心律失常作用。

Objective To investigate effects of 2-methylthio-adenosine-5＇-triphosphate （2-MeSATP）, which is an im- portant extracellular agonist that activates receptors for purine nucleotides （ P2XR）, on ventricular electrophysiological properties induced by congestive heart failure （CHF） in rabbits. Methods New Zealand rabbits were divide into control, CHF and 2-MeSATP groups. The CHF models were induced by injection isoproterenol （0.3 mg·~ kg-1 · d-1 for 3 weeks）,and justified successfully by observing clinic sign and pa- rameters of M echocardiography after 6 months. The main cardioelectrophysiological parameters and ventricular ar- rhythmias were tested by recording monophasic action po- tential （MAP） with programmed electrical stimulation and Burst-pacing in rabbits in vivo, so that determined RMP, APA, Vmax, APD20, APD50, APD90, as well as effectiverefractory periods （ERP） and ventricular arrhythmia inducibility. The transient outward potassium current （Ito） was recor- ded via whole-cell patch clamp technique in enzymatically dissociated single rabbit ventricular myocytes. And current-volt- age （I-V） curve was fit via current density as Y axis and command potential as X axis. Results Ten rabbits were en- rolled in each group. In CHF rabbits, RMP and APA were lower, and Vmax was slower as wall as APDs were all wider than that in control rabbit （all P〈0.05）. Compared with CHF group, RMP, APA and Vmax were significantly increased, APD20, APD50 and APD90 were shortened in 2-MeSATP group in vivo （all P 〈0.05）. On the other hand, compared with control group, ERP and basic cycle length （BCL） as well as persistence time inducing ventricular arrhythmias were significantly lengthened, and the rate of ERP/APD90 was severely decreased, and occurrence of ventricular arrhythmias were obviously increased in CHF group （all P 〈0.01 ）. However, ERP and BCL as well as persistence time of ventricular arrhythmias were obviously shortened, and rate of ERP/APD9o and inducibility of ventricular arrhythmias with programmed electrical stimulation and burst-pacing were decreased in 2-MeSATP group in vivo （all P〈0.01 ）. With voltage clamp model, com- pared with CHF group the current density of I,o were markedly increased, and I-V curve were upward in different command potential in 2-MeSATP. When holding potential was -50 mV and command potential was ＋50 mV, the current densities of Ito were significantly increased from （7.94±3.53）pA/pF in CHF group to （ 11.79±4.51 ）pAVpF in 2-MeSATP group（ P〈 0.01 ）. Conclusion 2-MeSATP as a potent agonist in CHF could significantly shorten APD, decrease the susceptibility of ventricular arrhythmias induced by CHF, which is contributed to anti-ventricular arrhythmias induced by CHF.