陈旧性心肌梗死对家兔动作电位时程跨室壁离散及L型钙电流的影响

探讨陈旧性心肌梗死 (MI) (MI后 3个月 ) ,远离MI中心区的心肌细胞电活动的改变。结扎家兔左前降支造成MI模型 ,3个月后酶解分离左室游离壁远离MI中心区的三层 (Epi、M、Endo)心肌细胞 ,采用全细胞膜片钳技术记录单细胞动作电位 (AP)和L型钙电流 (ICa ,L) ,并观察三层心肌细胞AP时程 (APD)的离散性 (TD APD)变化。结果 :MI后 3个月 ,远离MI区的三层心肌细胞的APD明显延长 ,其中Endo心肌细胞的APD明显短于Epi和M心肌细胞(P <0 .0 1)。陈旧性MI组 (OMI)与假手术组 (Sham)及对照组 (Control)比较 ,TD APD显著增加 (2 88.32± 19.5 6vs2 2 8.4 5± 13.94 ,2 10 .32± 17.4 3ms ,P <0 .0 1)。且在OMI组 ,ICa ,L的幅值增加 ,但密度降低 ,其中Endo的ICa,L密度降低最明显 (+10mV时 ,从 16 .12± 1.6 0降至 10 .73± 0 .0 6pA/pF ,降低了 33.4 3% ,Epi从 16 .5 9± 0 .5 0降至 11.75±0 .6 9pA/pF ,降低了 2 9.17% ,M细胞从 18.70± 1.0 3降至 13.2 7± 1.0 5pA/pF ,降低了 2 9.0 3% ,P <0 .0 5 )。结论 :MI3个月后远离MI区的心肌细胞ICa ,L密度明显降低 ,且以Endo降低最明显 ,三层心肌细胞的APD明显延长 ,并且En do心肌细胞的APD明显短于Epi和M心肌细胞 ,TD APD明显增加

Transmural Dispersion of Action Potential Duration and Heterogeneous Changes of L-Type Calcium Current in Rabbit Heart Three Months After Myocardial Infarction

During chronic,healed (three months) stage after myocardial infarction (OMI),structural and electrical remodeling of regions remote from the infarct plays an important role in arrhythmogenesis.We measured transmural dispersion of action potential duration (TD APD) in vitro,and studied changes of L type calcium current (I Ca,L ) of epimyocyte (Epi),midmyocyte (M) and endomyocyte (Endo) in region remote from infarcted zone.Results:We found that myocytes remote from infarct were hypertrophied and remodeled,APDs of three layers myocytes were lengthened,APD of Endo was shortest compared with Epi and M cell ( P <0.01).TD APD was significantly increased (OMI group 288.32±19.56 vs Sham group 228.45±13.94,Control group 210.32±17.43 ms, P <0.01).I Ca,L density was decreased in OMI group,the reduction of I Ca,L density was most prominent in Endo (at +10 mV,from 16.12±1.60 to 10.73±0.06 pA/pF,decreased 33.43% vs Epi from 16.59±0.50 to 11.75±0.69 pA/pF,decreased 29.17%,M from 18.70±1.03 to 13.27± 1.05 pA/pF ,decreased 29.03%, P <0.05).Conclusions:Our data suggest that the changes of TD APD and I Ca,L density in myocytes of region remote from infract zone are heterogeneous and are very susceptibility to develop reentrant arrhythmias.