莲心碱对心肌慢反应动作电位及慢内向电流的影响

EFFECTS OF LINESININE ON SLOW ACTION POTENTIALS IN MYOCARDIUM AND SLOW INWARD CURRENT IN CANINE CARDIAC PURKINJE FIBERS

莲心碱(Lien)10～100μmol/L可浓度依赖性地降低离体兔窦房结(SAN)起搏细胞慢反应动作电位幅度(APA)及零相最大上升速率((?)_(max)),延长窦性周长(SCL),并可明显拮抗Bay K 8644增大SAN起搏细胞及高K^-诱发的豚鼠乳头肌慢反应动作电位的APA和((?)_(max))作用。Lien 1～100 μmol/L还可浓度依赖性地抑制犬浦氏纤维慢内向电流(I_(si)),3和100μmol/L分别使I_(si)峰值下降14和88%。结果表明Lien具有抗钙作用。

Standard microelectrode and two-microelectrodes voltage clamp techniques were used to study the effects of linesinine(Lien), an alkaloid extracted from the green seed embryo of Nelumbo nucifera Gaertn, on slow action potentials (AP) and slow inward current (I_(si)). Lien 10～ 100 μmol/L was shown to concentration-dependently decrease the action potential amplitude (APA), the maximal velocity of phase O depolarization (V_(max)) and prolong the sinus cycle length (SCL) of slow AP in isolated sinoatrial node (SAN) pacemaker cells of rabbits. On both slow APs of rabbit SAN cells and guinea pig papillary muscles partly depolarized by high K^+, Bay K 8644 0.03 μmol/L markedly increased the APA and V_(max), which were obviously antagonized by Lien 10 μmol/L. Moreover, Lien 1～100 μmol/L was found to inhibit the I_(si) of canine cardiac Purkinje fiber in concentration—dependent manner. Lien 3 and 100 μmol/L reduced the peak value of I_(si) by 14% and 88% respectively. The results suggest that Lien possesses calcium antagonistic effects.