大鼠肺内动脉平滑肌细胞钾通道的研究

STUDY ON POTASSIUM CHANNELS OF RAT INTRAPULMONARY ARTERY SMOOTH MUSCLE CELLS

目的 研究大鼠肺内动脉平滑肌细胞钾电流。方法 用急性酶解分离法得到单个大鼠肺内动脉平滑肌细胞 ,采用膜片钳全细胞记录方式研究钾通道特性。结果 将平滑肌细胞钳制在 - 70mV ,给予 - 70～ 5 0mV的斜坡刺激 ,时间为 6 0 0ms。可引出一随电压逐渐增大的电流 ,在 + 5 0mV时其值为 35 9± 31pA。细胞内用CsCl取代KCl后 ,该电流几乎完全消失 ;细胞外用无钙台氏液灌流 ,电极内液用高浓度的EGTA时 ,电流可被抑制 5 0 %± 1% ;细胞外给予特异性钙激活钾通道阻断剂TEA和延迟整流钾通道阻断剂 4 AP均可使该电流明显下降。

AIM To study the potassium currents in rat intrapulmonary artery smooth muscle cells(SMCs). METHODS Using enzymatically isolated single SMCs and whole cell patch clamp techinique to record the potassium current. RESULTS Current clamp recordings were made with perforated patch to assess the mean resting membrane potential which was -48±5 mV ( n =9). Voltage clamp configurations were used to measure the membrane capacitance which was (27 9±1 2) pF( n =11). Outward potassium currents were evoked by using voltage ramps from -70 mV to +50 mV for a duration of 600 ms from a holding potential of -70 mV at the frequency of 0 1 Hz. The amplitude increased voltage dependently which reached (359±31) pA( n =32) at +50 mV. The currents were fully depressed when the KCl in the electrode was substituted by 130 mmol·L -1 CsCl. All the currents recorded with the external solution contained 1 2 mmol·L -1 Ca 2+ and the pipette solution contained a low concentration (1 mmol·L -1 ) of ethylene glycol bis (β aminoethyl ether) N,N,N′,N′ tetraacetic acid(EGTA), while removal of extracellular Ca 2+ and increase of the intracellular EGTA(from 1 mmol·L -1 to 10 mmol·L -1 ) reduced the current by 50%±1%. Specific calcium activated potassium channel and delayed rectifier potassium channel blockers 5 mmol·L -1 tetraethylammonium(TEA) and 4 aminopyridine(4 AP) can decrease the current from (12 52±1 08) pA/pF (control) to (6 75±1 54) pA/pF and from (13 99±1 11) pA/pF (control) to (9 38±2 36) pA/pF, respectively at +50 mV. CONCLUSION The whole cell potassium channel in the rat intrapulmonary artery smooth muscle cells consisted mainly of calcium activated potassium currents and delayed rectifier potassium currents recorded by voltage ramp patch clamp technique.