兔血管平滑肌延迟整流钾通道研究及其与克隆Kv1.5通道的电生理特性比较

STUDY ON DELAYED RECTIFIER K^+ CURRENT OF RABBIT VASCULAR SMOOTH MUSCLE CELLS AND COMPARISON WITH CLONED Kv1.5 CHANNEL

本文用膜片箝全细胞技术比较研究了单个兔肺动脉血管平滑肌细胞上延迟整流钾通道与克隆Kv1．5通道的电生理及药理学特性。将平滑肌细胞箝制在-40mV，以10mV的步距阶跃去极化（0～60mV）可产生一系列快速上升的外向电流，几无衰减，其激活曲线的V1/2为27．2mV。灌流液中加入100mmol／LTEA和1mmol／L 4AP，电流幅度均明显减小，细胞外Ca2+水平由1．5mmol／L降至0．5mml／L甚至0mmol／L时，该电流无明显改变。而在HBK7细胞（克隆Kv1．5通道），箝制在－80mV，以10mV的步距阶跃去极化（－30～＋60mV），可产生一系列的快速上升的外向电流，激活更快，无衰减，其激活曲线的V1/2为0．8mV。4AP抑制Kv1．5的IC50为7．3mmol／L，呈现频率和使用非依赖性；TEA30，100，300mmol／L分别使该电流幅度下降28.6％，37.4％，46．3％，Quinidine0．1和1mmol／L使其下降29．7％，37．6％。研究表明，我们记录到急性分离的免血管平滑肌细胞延迟整流钾通道，它的电生理及药理学特性与克隆的Kv1．5延迟整流钾通道存在明显差别。

Whole cell patch-clamp recorrding techniques were used to compare the electrophysiological properties between deayed rectifier K+ current of rabbit vascular smooth muscle cell(VSMC)and the cloned Kvl.5 channel.When VSMC is clamped at -40 mV,depolarizing the membrane potential at increasing steps of 10 mV could evoke a series of outward potassium cmrrents without any deactivation.The V1/2 of the activation curve was 27.2 mV.The curmnts decrease obviously after adding 100 mmol/L TEA or 1 mmol/L 4AP in the perfusate.When the concentration of extracellular Ca2+ was decreased from 1.5 mmol/L to 0.5 or 0 mmol/L,the currents did not show much change,while in HBK7(cloned Kv1.5 channel cell)held at-8O mV,similar steparise depolarizaton could also produce a series of outward potassium currents without any deactivation decayed.V1/2 of the activation was 0.8 mV.4AP inhibited the cloned channel current with IC50 of 7.3 mmol/L,showing neither frequency-or use-dependence.TEA(30,100 and 300 mmol/L)reduced the current by 28.6%,37.4% and 46.3% respectively.Quinidine(0.1 and 1 mmol/L)decreased it by 29.7% and 37.4%.These results show what we have recorded in isolated rabbit vascular smooth muscle cells is the delayed rectifier potassium currents which are different in electrophysiological and pharmacological properties from those of cloned Kv1.5 channel current.Supported by the National Foundation of Outstanding Young Scientists(No.39425014)