法乐四联症儿童肥厚右心室细胞瞬间外向钾电流的研究

目的观察压力增高导致的人肥厚心室组织离子通道的特性.方法应用酶解分离技术从法乐四联症(F4)患儿的心脏右室得到单个细胞,应用膜片钳全细胞记录技术观察了细胞Ito1的特征.结果将钙电流阻断后,去极化至-20mV～+60mV时均可记录到Itn1,激活后电流衰减速度不随去极化程度的增强而改变,在0、20、40、60mV时分别为123ms±6ms、131ms±10ms、122ms±6ms、122ms±6ms,去极化至60mV时的电流密度为4.7pA/pF±0.8pA/pF,半数最大激活电位为4.1mV±2.8mV,半数最大失活电位出现在-41mV±4mV,失活后再激活的恢复时间常数为83ms±4ms.这种电流可被10mM4-AP基本抑制.结论肥厚的人右室细胞存在Itn1,通道动力学特征与成人心房肌细胞类似.

Characterisation of transient outward potassium current (Itn1) in hypertrophied right ventricular myocytes frmm children with tetralogy of Fallot

OBJECTIVE: To investigate whether a transient outward potassium current exists in children hypertrophy ventricular myocytes and to characterize its basic electrophysiological properties. METHODS: Currents were recorded using whole-cell patch-clamp technique from enzymatically isolated ventricualr myocytes obtained from hearts of 10 patients aged 0.4-5 with tetralogy of Fallot (F4) ranging in age 0.4-5 years. RESULTS: In almost all cells studied, a Ito1 could be recorded on depolarization to between -20(-)+60 mV under conditions in which Ca2+ current was blocked. The current density is 4.7 PA/PF +/- 0.6 PA/PF at 60 mV. Its inactivation time constants under tested potential 0, 20, 40, 60 mV were 123 ms +/- 6 ms, 131 ms +/- 11 ms, 122 ms +/- 6 ms, 122 ms +/- 6 ms Half-maximal activation occurred at 4.1 mV +/- 2.8 mV. Half-maximal steady-state inactivation was -41 mV +/- 4 mV. Recovery from inactivation was voltage-dependent and the time course was 83 ms +/- 4 ms. CONCLUSION: A moderate Ca(2+)-independent transient outward K+ current is present in hypertrophied human ventricular myocytes from children with tetralogy of Fallot, its basic characteritics are similar to Ito1 observed in other species and human atria.