洛土辛对心肌动作电位及犬浦肯野纤维慢内电流的影响

目的　探讨洛土辛（Ｌｏｔ）对心肌动作电位（ＡＰ）及犬浦肯野纤维（ＰＦ）慢内向电流（Ｉｓｉ）的影响和其在正性肌力效应中所起的作用。方法　采用标准微电极及双微电极电压钳技术。结果　Ｌｏｔ１～１００μｍｏｌ·Ｌ－１可剂量依赖性地延长豚鼠乳头肌状快反应ＡＰ的ＡＰＤ２０和ＡＰＤ９０，增加收缩力（Ｆｃ）；在利血平化豚鼠乳头状肌，Ｌｏｔ对ＡＰＤ２０和Ｆｃ的影响较未经Ｒｅｓ化组减弱。在豚鼠左房肌，Ｌｏｔ３０μｍｏｌ·Ｌ－１可明显地削弱Ａｃｈ缩短ＡＰＤ５０和降低Ｆｃ的作用。Ｌｏｔ３～１００μｍｏｌ·Ｌ－１可剂量依赖性地增加高Ｋ＋去极化诱发的豚鼠乳头状肌及兔窦房结慢反应ＡＰ的ＡＰＡ、Ｖｍａｘ；对兔ＡＰＤ５０和窦房结周长（Ｓｉｎｕｓｃｙｃｌｅｌｅｎｇｔｈ，ＳＣＬ）却无明显影响。在犬ＰＦ，Ｌｏｔ３０μｍｏｌ·Ｌ－１时间依赖性及剂量依赖性地（３～１００μｍｏｌ·Ｌ－１）增加Ｉｓｉ。结论　Ｌｏｔ有延长ＡＰＤ和促钙内流作用，且在其正性肌力效应的产生中起着重要作用，而这些作用的产生与其抑制ＰＤＥⅢ有关。

Effects of lotusine on the action potentials in myocardium and slow inward current in cardiac purkinje fibers

AIM To study the effects of Lotusine(Lot), a pure alkaloid extracted from the green seed embryo of Nelumbo nucifera Gaertn, on the action potentials(APs) in myocardium and slow inward current(Isi) in cardiac Purkinje fibers(PF). METHODS standard microelectrode and two microelectrodes voltage clamp techniques were used. RESULTS Lot 1～100 μmol·L -1 could concentration dependently prolonged APD 20 and APD 90 of fast AP and increase the contractile force(Fc) in guinea pig papillary muscles. In papillary muscles pretreated with reserpine, similar results were also observed but the effect of Lot was weaker than those pretreated without reserpine. In guinea pig left atria, Lot 30 μmol·L -1 could partly antigoniste the shortening APD effect of acetylcholine. Lot 3～100 μmol·L -1 could enhance the action potential amplitude(APA)and maximal velocity of phase 0 depolarization ( V max ) of slow AP of papillary muscles induced by high K + (24 mmol·L -1 )and isolated sinoatral node(SAN) pacemaker cells of rabbits with dose dependent manner,But not obvousely short the sinus cycle length of SAN. Moreover, Lot increased the Isi of in canin cardiac PF with with time dependent and dose dependent manner. CONCLUSION The results suggest that Lot has effect of prolongation of APD and increase of Ca 2+ influx and these are very important in contribution to its positive inotropic effect, which may be related to inhibition of phosphodiesterase Ⅲ.