急性心肌缺血大鼠左心室流出道自发性慢反应电位去极离子流变化分析

Studies on Depolarized Ionic Flow of Spontaneous Slow Action Potential in Left Ventricular Outflow Tract in Rats with Acute Myocardial Ischemia

目的探讨急性心肌缺血大鼠左室流出道自发性慢反应电位去极离子流的变化。方法常规玻璃微电极细胞内方法观测急性心肌缺血大鼠的离体心脏最大舒张电位(MDP)、0相除极幅度(APA)、0相最大除极速度(Vmax)、4相自动除极速度(VDD)、复极50%(APD50)和90%(APD90)的时间以及自发放电频率(RPF)。结果与给药前相比①1.2mmol.L-1河豚毒(TTX)使APA和Vmax有所减小(P<0.05),VDD和RPF明显减慢(P<0.01);②1.0μmol.L-1维拉帕米(VER)可使该慢电位的APA、Vmax、VDD明显减小,RPF减慢(P<0.01);APD、APD90延长(P<0.05);③2mmol.L-1 4-氨基吡啶(4-AP)使该慢电位的MDP的绝对值、APA、Vmax减小,VDD和RPF加快(P<0.01);④1.5mmol.L-1 CsCl作用6min时,VDD和RPF明显降低(P<0.05),10min时恢复。结论①左心室流出道的自发慢电位0相主要去极离子流除Ca2+内流外,还有少量Na+内流。②4相去极离子流中,除Ca2+、Na+的内流和Ik衰减外,If电流可能也起部分作用。

Objective To analyze the depolarized ionic mechanism for slow-response action in left ventricular outflow tract in rats with acute myocardial ischemia.Methods Spontaneous slow action potentials of left ventricular outflow tract were intracellularlly recorded with conventional microelectrodes.Electrophysiological parameters were maximal diastolic potential(MDP),amplitude of action potential(APA),maximal rate of depolarization of phase 0(Vmax),velocity of diastolic depolarization of phase 4(VDD),duration of 50% and 90% repolarization(APD50 and APD90)and rate of pacemaker firing(RPF).Results ①1.2 mmol·L-1 tetrodotoxin(TTX)significantly decreased APA and Vmax(P&lt;0.05),while VDD and RPF were significantly slowed down as compared with that of controls(P&lt;0.01).②1.0 μmol·L-1 verapamil(VER)significantly decreased APA,Vmax,VDD and RPF,(P&lt;0.01),with APD and APD90 significantly prolonged.③2 mmol·L-1 4-aminopyridine(4-AP)decreased MDP,APA and Vmax(P&lt;0.01),while VDD and RPF increased(P&lt;0.01).④1.5 mmol·L-1 CsCl perfused for 6 min significantly decreased VDD and RPF(P&lt;0.05).Conclusion The data suggest that:①Generation of 0 phase of depolarization for slow-response activity in aortic vestibule from spontaneously hypertessive rats was mainly mediated by Na+ current and Ca2+.②In addition to inward Ca2+ and Na+ current and attenuated K+ current,If current also plays part role in phase 4 depolarization.