苄基四氢巴马汀细胞内用药对豚鼠乳头状肌动作电位和心室肌细胞延迟整流钾电流的作用

目的　研究将苄基四氢巴马汀(BTHP)导入细胞内对豚鼠乳头状肌动作电位及单个心室肌细胞延迟整流钾电流的影响。方法　利用外加电压脉冲将药物导入乳头状肌细胞内，并用标准微电极方法测定动作电位；利用浓度差扩散方式使药物进入单个心室肌细胞内，采用全细胞膜片钳技术记录延迟整流钾电流（I_K）。结果　100 μmol.L^-1 BTHP使APD₂₀和APD₉₀分别延长13.5%和20.5%。30 μmol.L^-1 BTHP使I_K和I_K,tail分别从（14.1±2.2) pA.pF^-1和(4.0±0.6) pA.pF^-1降至(9.4±1.3) pA.pF^-1和(2.1±1.0) pA.pF^-1，下降率分别为33.2%和35.3%。 该药使I_K和I_K,tail的I-V曲线幅度降低，对曲线形状影响不明显。结论　BTHP入细胞内后可阻滞延迟整流钾电流和延长动作电位时程。

INTRACELLULAR EFFECTS OF BENZYLTETRAHYDROPALMATINE ON THE ACTION POTENTIAL AND DELAYED RECTIFIER POTASSIUM CURRENTS IN GUINEA PIG PAPILLARY MUSCLE AND VENTRICULAR MYOCYTES

AIM　To investigate the effects of benzyltetrahydropalmatine (BTHP) on the action potential (AP) of guinea pig papillary muscle and delayed rectifier potassium currents (I_K )of single ventricular myocyte when administered intracellularly. METHODS　Standard microelectrode was applied to examine the characteristics of the AP. BTHP included in the pipette internal solution was dialyzed into papillary muscle cell by using a pulse with duration of 50 ms, voltage of +40 V. The parameters of AP were recorded after 20 min of intracellular dialysis. Whole cell patch clamp technique was used to measure the I_K and BTHP was applied intracellularly in single ventricular myocyte by cell dialysis method. RESULTS　100 μmol.L^-1 BTHP prolonged APD20 and APD90 by 13.5% and 20.5%, respectively. Furthermore, 30　μmol.L^-1 BTHP was demonstrated to decline I_K and I_K,tail from (14.1±2.2) pA.pF^-1 and (4.0±0.6) pA.pF^-1 to (9.4±1.3) pA.pF^-1 and (2.6±1.0) pA.pF^-1 with inhibition rates of 33.2% and 35.3%, respectively. BTHP reduced the amplitude of I-V curves of I_K and IK,tail, but did not affect the shape of them significantly. CONCLUSION The results showed that BTHP used intracellularly can block IK and prolong the duration of action potential(APD).