Studies on the calcium antagonistic action of tetrandrine: X VI. Effects of tetrandrine on positive staircase phenomenon and post-rest potentiation of contraction of isolated guinea pig left atrium

Summary Tetrandrine (Tet) 0.32 mmol/1 and verapamil (Ver) 30 μmol/1 inversed positive staircase phenomenon of contraction in left alrium of guinea pig. After the preparation was partially depolarized with K₊ 20 mmol/1, such effect of Tet and Ver became much more pronounced. Propranolol could not inverse the positive staircase phenomenon. In addition, after treatment with Tet 0.32 mmol/1 for 20 min the post -rest potentiation of myocardial contraction in the left atrium was depressed by 2.8±0.3 g (P<0.01). The results suggest that the negative inotropism of Tet is related not only to the inhibition of Ca⁺⁺ influx to the cells, but also to the decrease of the intracellular Ca⁺⁺ release.     

Studies on the calcium antagonistic action of tetrandrine: VIII. Antagonistic effects of tetrandrine on ouabain-induced contraction of coronary arterial strips

Summary The antagonistic effects of tetrandrine (Tet) on ouabain-induced contraction were studied in swine coronary arterial strips. Like verapamil (Ver), the contraction evoked by ouabain (Oub) 0.85 μM, the synergistic effect of Oub 85 nM and Ca⁺⁺ 2–16 mM, and the response to electrical stimulation in the presence of Oub 85 nM were all inhibited by Tet (10 μM-1.2 mM), although these effects were less potent than those of Ver. All these pharmacological actions of Tet and Ver were reversed by the addition of extra Ca⁺⁺ to the bathing medium. The results we obtained confirm that Tet is a Ca⁺⁺-antagonist of plant origin.     

Studies on the calcium antagonistic action of tetrandrine: VI. Comparison of effects of tetrandrine,verapamil and propranolol on myocardial blood flow

Summary By⁸⁶RbCl-extraction method, the effects of tetrandrine (Tet), verapamil (Ver) and propranolol (Pro) on myocardial blood flow of mice were studied. Both I.P. Tet 100 mg/kg and Ver 5 mg/kg increased the blood flow, whereas I.P. Pro 30 mg/kg did not. Pro counteracted significantly the increase of myocardial blood flow by isoproterenol, while Tet and Ver failed. On the other hand, Tet and Ver markedly antagonized the increase of myocardial blood flow by CaCl₂, but Pro did not. The results indicate that unlike the β-receptor blocking agent Pro, Tet may be a calcium antagonist similar to Ver.     

Studies on the calcium antagonistic action of tetrandrine: XVI. Hemodynamic effects of tetrandrine on conscious rats

Hemodynamic study of tetrandrine (Tet) in conscious rats showed that 15 mg/kg i.v. lowered BP, LVSP, ±dp/dt_max , and (dP/dt)P⁻¹. The degree of diminutions was nearly equal to that of BP during the initial period, while the LVEDP was elevated. But all these parameters (except −dp/dt_max ) recovered gradually and earlier than BP, and LVEDP decreased to a level slightly lower than that of control. These results indicate that the hypotensive action of Tet is mainly due to its inhibition of cardiac contractility at the early period, but due to vasodilatation in the later stage. The HR was slowed down abruptly followed by a reflex acceleration, and than a gradual but sustained decrease in HR supervened with i.v. Tet. When large dose (40 mg/kg) of Tet i.v. caused a cardiac standstill with the R wave of ECG persisting for a few minutes, it means that an excitation-contraction decoupling occurred as that found on isolated myocardial preparation treated with verapamil and Tet.     

Effects of benactyzine on action potentials and contractile force of guinea pig papillary muscles

ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｎａｃｔｙｚｉｎｅｉｓａｓｙｎｔｈｅｔｉｃｂｌｏｃｋｅｒｏｆＭ ｒｅｃｅｐｔｏｒｐｏｓ ｓｅｓｓｉｎｇｓｍｏｏｔｈｍｕｓｃｌｅｒｅｌａｘａｎｔｐｒｏｐｅｒｔｉｅｓａｎｄｑｕｉｎｉｄｉｎｅ ｌｉｋｅａｃｔｉｏｎｏｎｈｅａｒｔ[1] .Ｂｅｎａｃｔｙｚｉｎｅｉｓｅｆｆｅｃｔｉｖｅｉｎｒｅｓｔｏｒ ｉｎｇｃｉｒｃｕｌａｔｏｒｙｆｕｎｃｔｉｏｎｄｉｓｔｕｒｂｅｄｂｙｏｒｇａｎｏｐｈｏｓｐｈａｔｅｐｏｉ ｓｏｎｉｎｇ[2 ,3] .Ｐｒｅｖｉｏｕｓｓｔｕｄｉｅｓｓｕｇｇｅｓｔｅｄｔｈａｔｂｅｎａ…     

哇巴因和乌头碱对豚鼠和大鼠心肌细胞钠电流的作用

目的 观察哇巴因和乌头碱对豚鼠和大鼠心肌细胞钠电流的作用,探讨二药诱发心律失常的机制.方法 用全细胞膜片钳技术分别记录豚鼠和大鼠单个心肌细胞钠电流.结果 在-40mV电压下,哇巴因5μmol/L使Ina从(-48.3±8.9)pA/pF减少到(-22.6±5.6)pA/pF(抑制60.1%,n=5,P＜0.01);乌头碱1μmol/L使Ina从(-21.8±5.8)pA/pF增加到(-67.3±7.8)pA/pF(增加208.7%,n=4,P＜0.01).结论 哇巴因抑制豚鼠心肌细胞钠电流而乌头碱增加大鼠心肌细胞钠电流.不论是抑制还是促进钠电流,二药均使离子通道失衡,这是其诱发心律失常的重要机制.     

Effect of tetrandrine on cellular electrophysiology and calcium uptake of myocardium in guinea pigs and dogs

目的　本文旨在研究汉防已甲素对豚鼠及狗的心肌动作电位 (AP)、收缩力及肌浆网钙吸收的作用。方法　用玻璃微电极的方法 ,研究用药后心肌细胞AP、dV/dt、峰张力 (PT)及dT/dt等指标的改变 ,并用生化方法估价用药后心肌肌浆网钙吸收率及无机磷释放等指标的变化。结果　汉防已甲素起着浓度依赖性和频率依赖性负性变力性作用 ,且缩短了动作电位时程。汉防已甲素抑制心肌dT(E) /dt和dT(L) /dt,也抑制了心肌张力 ,并降低了慢动作电位的dV/dt和幅度 ,这些暗示汉防已甲素可阻止慢钙通道。另外 ,与Thapsigargin(一种特异性肌浆网Ca2 ATP酶抑制剂 )进行了比较 ,汉防已甲素较之更为明显地抑制了心肌的收缩。结论　汉防已甲素是一种植物性广谱钙离子拮抗剂。它不仅阻止电压操纵的钙通道 (象其它作者所报导的那样 ) ,而且在影响Ca2 ATP酶及肌浆网钙释放通道方面也起着重要的作用。我们的资料提示钙通道对心肌收缩似乎比肌浆网更为关键。     

维拉帕米、美托洛尔停搏液对离体大鼠心肌的保护作用

目的 观察三种停搏液的保护心肌效果,并对共效应进行对比研究。方法 应用改良的Ｌａｎｇｅｎｄｏｒｆｆ离体大鼠心脏灌注装置,分别灌注三种冷停搏液,Ｓｔ ＴｈｏｍａｓⅡ号停搏液（Ⅰ组）、ＳＴⅡ号＋维 １ｍｇ／Ｌ（Ⅱ组）,ＳＴⅡ号＋美托洛尔０．１ｍｇ／Ｌ（Ⅲ组）,比较三组心肌保护效果。结果 Ⅱ组、Ⅲ组心肌缺血再灌注后心肌含水率、心 主超微结构损伤明显轻于Ⅰ组,冠脉流量恢复率明显高于Ⅰ组。结论 维拉帕米、美     

pH值对川芎嗪在豚鼠心肌电生理-机械特性的影响中的作用

目的：观察调节ｐＨ至７．４的川芎嗪与不调节ｐＨ的川芎嗪对豚鼠心室乳头状肌电生理－机械特性的影响。方法：常规电生理方法,标准玻璃微电极技术。结果：①调节 ｐＨ至 ７．４与不调节 ｐＨ的低浓度川芎嗪（３．０～ ３０μｍｏｌ）均使豚鼠乳头状肌慢反应电位（ＳＡＰ）的动作电位幅值（ＡＰＡ）,动作电位时程（ＡＰＤ）,最大除极速度Ｖｍａｘ及收缩力（ＦＣ）呈剂量依赖性抑制;②调节ｐＨ至７．４的高浓度川芎嗪（０．１～３．０ ｍｍｏｌ／Ｌ）使豚鼠乳头状肌 ＳＡＰ的 ＡＰＡ、ＡＰＤ、Ｖｍａｘ及ＦＣ呈剂量依赖性增强;而不调节ｐＨ的高浓度川芎嗪（０．１～３．０ ｍｍｏｌ／Ｌ）使豚鼠乳头状肌ＳＡＰ的ＡＰＡ、ＡＰＤ、Ｖｍａｘ及ＦＣ呈抑制效应。结论：①川芎嗪对豚鼠心肌电生理－机械特性有双重影响作用,即低浓度抑制,高浓度增强。②川芎嗪本身的酸性影响川芎嗪对豚鼠心肌电生理－机械特性的正性作用。