绝对不应期电刺激对心力衰竭豚鼠心室肌细胞动作电位时程和L型钙电流的影响

目的 探讨绝对不应期电刺激(ARPES)对健康和心力衰竭豚鼠心室肌细胞(分别简称NVM和FVM)动作电位(AP)时程(APD)和L型钙电流(ICa-L)的影响。方法 应用膜片钳技术中电流钳,首先记录基础刺激S1所诱发的AP(APS1),与S1延迟10 ms给予ARPES,记录ARPES给予后的AP(APARPES),比较APS1和APARPES的APD的值,以APD30、APD50和APD90代表动作电位复极30%、50％和90％时的APD值。分别以APS1和APARPES为测试电压,记录AP电压钳下的细胞膜ICa-L。结果(1)在NVM和FVM,ARPES应用后APD均明显延长,以APD30和APD50最为显著(P<0.01)。(2)在NVM,与APS1电压钳记录的ICa-L相比,APARPES电压钳记录的ICa-L电流强度有一过性的减弱和继发增强,但其单位膜电容下的电流强度的整合值略有降低(P<0.05)。在FVM,与APS1电压钳记录的ICa-L相比,APARPES电压钳记录的ICa-L电流强度的减弱程度明显减少,其单位膜电容下的电流强度的整合值是增加的(P<0.01)。结论 ARPES延长NVM和FVM的APD,对NVM和FVM的ICa-L具有不同的影响。

Effects of electrical stimulation applied during absolute refractory period on action potential duration and L-type calcium channel currents of ventricular myocytes from normal and failing guinea-pigs

Objective To investigate the effects of electrical stimulation (ES) applied during absolute refractory period (ARP) on the action potential (AP) duration (APD)and L-type calcium channel currents(ICa-L) of normal and failing ventricular myocytes(NVM and FVM respectively) from guinea-pigs. Methods AP tracings were recorded by whole-cell membrane current clamp when they were elicited either by only base stimulation S1 (APS1) or by additional ARPES given in 10 ms after S1 stimulation (APARPES). APD measured from APS1 and APARPES respectively were compared each other,and APD30, APD50 and APD90 represented the APD when 30% ,50% and 90% of AP were repolarized respectively. ICa-L were recorded by whole-cell membrane voltage clamp in the form of APS1 and APARPES clamp respectively. Results (1) The APD were extended obviously after the ARPES was given in both normal and failing guinea-pig ventricular myocytes, in which the APD30 and APD50 was the most striking one among APD30, APD50 and APD90 (P < 0. 01). (2) The ascending part of ICa-L (representing its inactivation period) elicited by APARPES was different from that elicited by APS1 , whereas the total Ca2 influx by integrating the current records decreased a little in NVM(P<0. 05) , and the integrated current records during APARPES clamp increased in FVM(P <0. 01) compared with those during APS1 clamp. Conclusion ARPES prolonged APD of ventricular myocytes from both normal and failing guinea-pigs, and had different effects on ICa-L of NVM and FVM.