心肌梗死后神经过度增生对心肌动作电位影响的膜片钳研究

Effect of Increased Nerve Proliferation on Action Potential of Single Myocyte in Rabbit Heart With Healed Myocardial Infarction Using Patch Clamp Technique

为探讨心肌梗死 (简称心梗 )后神经过度增生对心肌细胞动作电位 (AP)的影响 ,1 8只兔随机分为三组 ,神经生长因子 (NGF)组结扎左回旋支并通过皮下置管于左侧星状神经节 ,给予NGF 4 0 0U ,共 30d。陈旧性心梗 (HMI)组结扎冠状动脉左回旋支和皮下置管 ,假手术 (Sham)组皮下置管和开胸但不结扎冠状动脉 ,3个月后应用膜片钳技术记录心外膜下心肌细胞AP。结果 :HMI组心肌细胞的膜电容较Sham组增加 1 9% ,而NGF组的膜电容较HMI组增加 2 2 % (P <0 .0 5 )。NGF组非梗死区 (NIZ)的心肌细胞的动作电位时程 (APD)较HMI组和Sham组明显延长 ,P <0 .0 5 ;而NGF组梗死周边区 (IBZ)的心肌细胞的APD与HMI组相近 ,均较Sham组明显缩短 ,P <0 .0 5。NGF组中NIZ与IBZ间心肌细胞APD的复极离散 (DR) ,较HMI组和Sham组明显增加 ,P <0 .0 5。NGF组的NIZ早期后除极的发生率为 6 3.2 % (1 2 / 1 9) ,HMI组为 1 6 .7% (3/ 1 8) ,Sham组为 0 % (0 / 2 0 )。结论

In this study, we investigate the effect of increased nerve proliferation on action potential of single myocyte in rabbit heart with healed myocardial infarction using patch clamp technique.18 rabbits were randomly assigned three groups: NGF group, ligation of the circumflex coronary and polyethylene pipe placed to left satellite ganglion in subcutis of neck for administration of nerve growth factor(NGF) 400U×30d ; HMI group, ligation of the circumflex coronary and subcutaneous placement of polyethylene pipe; Sham group, subcutaneous placement of polyethylene pipe and left thoracotomy but no coronary ligation. After 3 monthes, the rabbits were sacrificed for measurement of action potential of single myocyte from subepicardium with patch clamp technique. Results: The membrane capacity of myocyte in HMI group increased by 19% compared with that in Sham group. Moreover, the menbrane capacity of myocyte in NGF group increased 22% by compared with that in HMI group(P<0.05). Action potential duration (APD) of myocyte from remote zone from the infarct (NIZ)in NGF group was prolonged compared with those in HMI group and Sham group respectively,P<0.05; APD of myocyte from infracted border zone (IBZ)in NGF groupwas similar to that in HMI group. They were significantly shorter than that in Sham group,P<0.05. Repolarization dispersion between NIZ and IBZ in NGF group was 436±57 ms, which increased significantly compared with those in HMI group and Sham group respectively, P<0.001. The prevalence of early after depolarization was 63.2%(12/19)in NIZ of NGF group, 16.7%(3/18)of HMI group, 0%(0/20) of Sham group. Conclusion: Increased dispersion of repolarization and more early after depolarization in NGF group are responsible for the decreased VFT.