赛庚啶对豚鼠心室肌细胞钙电流的影响

应用全细胞记录式膜片钳技术研究了赛庚啶(Cyp)对豚鼠心室肌细胞慢钙电流(I_(Ca))的影响,Cyp 3和8μmol·L~1对I_(Ca)的电流-电压关系曲线(I-V曲线)之各电流均有降低作用,使I-V曲线上抬;在指令电位0 mV时,I_(Ca)为次最大值,Cyp 0.3～10μmol·L~1使该I_(Ca)呈浓度依赖性降低,IC_(50)值为1.98μmol·L~1,还观察到Cyp 1μmol·L~1明显增加外向电流(I_(out)),且四乙基铵(TEA)1 mmol·L~1对其有显著的拮抗作用,但对控制电位从80 mV跃升至-40 mV时所出现的瞬时快内向电流,无明显影响.以上结果直接证明了Cyp对心室肌细胞钙跨膜转运有明显降低作用,还可能增加钾外流。

Effects of cyproheptadine on Ca~(2+)current in guinea pig ventricular myocytes

The effects of cyproheptadine(Cyp)on the slow Ca2+ currents(ICa)in a single guinea pig ventricular myocyte were studied using the whole cell recording patch clamp technique.Superfusion of cells with Cyp(3 and 8μmol·L-1)showed the inhibition of all the ICa which was elicited by depolarization from-30mV to +30 mV at 0.2 Hz and the uprising of current-voltage relationship curves(I-Vcurve).The I-V curve for ICa showed the next maximum values at 0 mV.This ICa was decreased by Cyp 0.3-10μmol·L-1 in a concentration-dependent manner.The half inhibition concentration(IC50)of Cyp was 1.98μmol·L-1 It has been observed that Cyp 1μmol·L-1 markedlyincreased the amplitude of outward current(Iout),while tetraethylammonium(TEA)exerted a significant antagonistic action on it.But on the fast inward current which had been elicited by a depolarization step from-80 mV to-40 mV,Cyp had no or little effect.The results demonstrate that Cyp depresses the transmembrane calcium current and may also enhance the K+ outward current in the ventricular myocytes.