溶血磷脂酰胆碱对缺血条件下羊浦肯野纤维I_f电流的影响

EFFECT 0F LYSOPHOSPHATIDYLCHOLINE ON THE PACEMAKER CURRENT I_f OF SHEEP CARDIAL PURKINJE FIBERS IN ISCHEMIA-LIKE CONDITION

本文用双微电极电压箝制术观察“缺血”及毒性代谢产物溶血磷脂酸胆碱（LPC）对绵羊心室浦肯野纤维起搏离子流If的影响。用模拟缺血溶液灌流15，30和60min后，在一60mV～120mV之间的各不同指令电位水平If离子流幅值均降低（n=5，P＜0．05），激活达稳态时间及半激活时间延长（n=5，P＜0．05），稳态激活曲线向超极化方向移位。在正常台氏液中加入2×10-5mol/LIPC，灌流后，各个膜电位水平的浦氏纤维起搏离子流If的幅值显著降低（n=10，P＜0.05），稳态激活曲线向超极化方向移位，但If激活达稳态时间及半激活时间均无明显改变。在模拟缺血溶液灌流30min基础上，再加2×10－5mol／LLPC灌流，15min后测得If幅值进一步减小（n=10，P＜0．05），加剧了“缺血”对If离子流的抑制作用。上述结果表明：缺血代谢产物溶血磷脂酸胆碱对心室的正常自律活动具有抑制作用，在模拟缺血条件下，它能使已受抑制的自律活动抑制进一步加深。因此它的存在不会异常增强心室自律性活动而发生快速性室性心律失常。

By using two microelectrode voltage clamp technique, the effects of 'ischemia' and lysophosphatidylcholine (LPC), a main toxic metaboli te in acute ischendic myocardium,on pacemaker current If were examined in sheep cardiac Puri nje fibers. Afer perfusion with ischemia-like solution for 15, 3O and 60 min, the amplitude of If current was decreased at all meInbrane potential levels between - 60 mV ～- 120 mV (n = 5, P <0. 05), both the activation time and half activation time reaching a steady state value were prolongated (n = 5, P < 0. 05), with a result of shifting activation curve of If to a more hperpolarizing level- In normal Tyrode s0lution, the amplitudes of If at all measured potential levels .ere' decreased significantly by irC 2 x lO-5 moUL (n = 10, P <0.05); the steady-5tate activation curve of If was shifted to a more hyperpolarizing level but the activation time and half activation time to a steady-state value were not changed.When 2 × 10-5 mol/LPC was added to the solution after 30 min 'ischemia', the amplitude of If decreased significantly at all measured membrane potentials and further more for another 15 min (n = 10, P < 0.05 ). This suggests that ischemic metabolite LPC may have an inhibitory effect on the normal pacemaker activity of ventricle.Ischemic-like condition could aggrvate the suppression of LPC without inducing abnormal strengthening of normal automatic rhythmic activity that might lead to ventriculartachyarrhythmia.