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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。
Objective To investigate the effect of Lotusin on myocardial action potential (AP) and canine Purkinje fiber (PF) slow inward current (Isi) and its role in positive inotropic effect. Methods Standard microelectrode and double microelectrode voltage clamp technique were used. Results Lot 1～100 μmol·L-1 dose-dependently prolonged the APD20 and APD90 of AP in guinea pig papillary muscles and increased the contractile force (Fc); the effect of Lot on APD20 and Fc in the papillary muscles of guinea pigs It is weaker than the non-Res group. In the left atrial muscle of guinea pigs, Lot 30 μmol·L-1 significantly attenuated the effect of Ach shortening APD50 and decreasing Fc. Lot 3～100 μmol·L-1 dose-dependently increased the APA, Vmax of slow-response AP in the guinea pig papillary muscles and rabbit sinus node induced by high K+ depolarization; the rabbit APD50 and sinus node length (SCL) ) But no significant effect. Isi was increased in a time-dependent and dose-dependent manner (3 to 100 μmol·L-1) in dog PF and Lot 30 μmol·L-1. Conclusion Lot has prolonged APD and calcium influx, and plays an important role in the production of inotropic effect. The production of these effects is related to the inhibition of PDEIII.