III类抗心律失常药RP58866对豚鼠及犬内向整流及瞬时外向钾电流的作用

目的:研究III类抗心律失常药RP58866 对I_K1 ,瞬时外向钾电流(Ito) 的作用。方法:用豚鼠和犬离体心肌细胞及全细胞电压钳技术。结果:在- 100 m V 时,RP58866 以浓度依赖方式明显减少了豚鼠心室肌细胞I_K1,其IC₅₀为(3-4±0-8) μmol·L^-1。在犬心室肌细胞,RP58866 可明显抑制Ito( 在100 μmol·L^-1 时减少87% ±2-1% ),其IC₅₀为(2-3±0-5) μmol·L^-1 。结论:RP58866 对心肌细胞的IK1 和Ito 均有抑制作用,而不是一种特殊的IK1抑制剂。     

4-氨基吡啶对豚鼠心室肌钙和钠电流的影响

目的研究4-氨基吡啶(4-AP)对心肌细胞L型钙通道和钠通道的影响。方法用全细胞膜片钳技术考察4-AP对豚鼠心室肌细胞L型钙电流和钠电流的作用。结果4-AP0.1,0.5,1.0mmol·L^-1浓度依赖性地抑制L型钙电流(I_Ca,L)和钠电流(I_Na),抑制率分别为(11.6±1.7)%,(37.5±8.3)%和(54.5±6.9)%以及(22.1±14.3)%,(39.4±8.8)%和(62.3±6.8)%。0.5mmol·L^-14-AP使I_Ca,L和I_NaI-V曲线均上移。结论4-AP可浓度依赖性地阻滞豚鼠心室肌细胞L型钙通道和钠通道。     

阿米洛利对豚鼠心肌细胞钾电流及钙电流的作用

目的研究阿米洛利（amiloride）对豚鼠心肌细胞钾电流及钙电流的作用。方法采用全细胞膜片钳技术记录豚鼠心室肌细胞钾通道及钙通道电流。结果阿米洛利在10~100 μmol·L^-1抑制L型及T型钙电流,不改变钙电流I-V曲线的形状，仅抑制这两型电流的幅度。当累积浓度达100 μmol·L^-1时，阿米洛利轻微抑制快激活延迟整流钾电流(I_Kr)，对慢激活延迟整流钾电流(I_Ks)无影响。阿米洛利在1~100 μmol·L^-1浓度依赖性地抑制内向整流钾电流(I_K1)。结论阿米洛利抑制电压依赖性的钾、钙电流，为其抗心律失常作用提供了离子基础。     

钾通道阻断剂部分抑制三氧化二砷诱导的HeLa细胞死亡

目的研究钾通道阻滞剂对三氧化二砷诱导的HeLa细胞死亡的作用。方法采用MTT法评价HeLa细胞的存活情况，采用膜片钳技术记录HeLa细胞的电压依赖性钾电流。结果As₂O₃(5 μmol·L^-1)孵育24 h引起显著的HeLa细胞死亡，As₂O₃(5 μmol·L^-1)孵育24 h后存活的细胞表现明显的电压依赖性钾电流密度增加。+80 mV电压下，As₂O₃(5 μmol·L^-1)孵育组电流密度(61±18) pA/10 pF(n=8)明显高于对照组(38±10) pA/10 pF(n=8,P<005)。As₂O₃诱导的HeLa细胞死亡可被共同孵育钾通道阻滞剂四氨基吡啶(3 mmol·L^-1)或四乙基铵(5 mmol·L^-1)所部分抑制。3 mmol·L^-1四氨基吡啶或5 mmol·L^-1四乙基铵对HeLa细胞无明显细胞毒作用。结论As₂O₃长期处理增加HeLa细胞的电压依赖性钾电流。As₂O₃诱导的HeLa细胞死亡可被钾通道阻滞剂四氨基吡啶或四乙基铵部分抑制。     

粉防己碱、颅通定对兔窦房结动作电位及豚鼠心室肌单细胞钙电流的协同作用

采用标准微电极技术和膜片钳记录技术,分别研究了粉防己碱(Tet)和颅通定(rotundine)对家兔窦房结动作电位及豚鼠心室肌单细胞钙电流的影响。结果表明:Tet1～200μmol·L^-1,rotundine3～300μmol·L^-1能浓度依赖性地降低兔窦房结动作电位的APA,Vmax和SP₄,延长SCL。Tet0.3μmol·L^-1与rotundine1μmol·L^-1合用亦有作用。在膜片钳实验中Tet0.1μmol·L^-1和rotundine1μmol·L-1合用能有效抑制豚鼠心室肌单细胞钙电流,抑制率为19.2%。提示,两种植物源性抗钙剂有良好的协同效果。     

双苯氟嗪对异丙肾上腺素所致早后除极和触发活动的影响

用异丙肾上腺素(Iso)诱发豚鼠右心室乳头肌产生早后除极(EAD)和触发活动(TA), 通过细胞内微电极技术,观察双苯氟嗪(Dip)对EAD和TA的预防作用. 在0.5 Hz刺激频率下, 50 nmol·L^-1 Iso在延长动作电位时程的基础上, 可诱发豚鼠乳头肌产生EAD, 并出现TA, 有时TA会发展成持久的节律性活动, 有的还伴有EAD或迟后除极. Dip 3和10 μmol·L^-1可显著降低Iso诱发的EAD波幅及发生率和TA发生率; Dip 10 μmol·L^-1还明显延长TA潜伏期. 结果提示, Dip能预防, 减少或延迟Iso引起的豚鼠乳头肌EAD和TA.     

用β-escin穿孔膜片技术研究粉防己碱对豚鼠心室肌钙电流的作用

目的用β-escin穿孔膜片(PPR)技术研究粉防己碱(tetrandrine,Tet)对I_Ca,L和I_Ca,T的作用。方法用PPR和全细胞记录(WCR)模式记录心室肌细胞I_Ca,L和I_Ca,T。结果25 μmol·L^-1 β-escin可在心室肌细胞形成稳定的PPR模式,用此模式记录的I_Ca,L衰减明显减慢。在PPR模式下1～300 μmol·L^-1 Tet浓度依赖性地减小I_Ca,L幅值。3,30和300 μmol·L^-1 Tet对I_Ca,T的抑制率分别为(16±5)%,(40±7)%和(75±11)%。结论用25 μmol·L^-1 β-escin在豚鼠心室肌细胞能得到较稳定的PPR模式,在此模式下Tet浓度依赖性地抑制I_Ca,L和I_Ca,T。     

格列美脲蛋白结合作用的高效液相色谱-迎头分析法

目的研究格列美脲与人血清白蛋白(human serum albumin,HSA)结合作用。方法采用高效液相色谱-迎头分析法(high performance liquid chromatography-frontal analysis, HPLC-FA)。色谱柱为内表面反相(internal-surface reversed-phase,ISRP)硅胶柱Pinkerton GFF II-S5-80(150 mm×4.6 mm ID, 5 μm)；流动相为 67 mmol·L^-1磷酸盐等渗缓冲液 (pH 7.4, I=0.17 mol·L^-1)；流速0.2 mL·min^-1；检测波长230 nm；进样量900 μL；柱温37 ℃。结果 应用非线性回归参数估算求得HSA分子上两类结合位点结合的格列美脲分子数及相应的结合平衡常数：n₁=1和K₁=5.1 (μmol·L^-1)^-1；n₂=7和K₂=0.017 (μmol·L^-1)^-1。结论HPLC-FA法操作简便，适用于研究格列美脲与HSA的结合作用。     

5-单硝酸异山梨酯对兔离体隐动脉交感嘌呤能缩血管反应的影响

采用兔离体隐动脉血管环张力实验及电场刺激诱发交感嘌呤能血管收缩实验，观察5-单硝酸异山梨酯(isosorbide-5-mononitrate，ISMN)对交感嘌呤能缩血管反应的作用，并分析其作用机制。结果表明，电场刺激(电压15 V，波宽1 ms，时程1 s)诱发兔离体隐动脉(去内皮)产生血管收缩反应。该收缩反应呈频率(2～16 Hz)依赖性，可被0.1 μmol·L^-1河豚毒素(tetrodotoxin)完全抑制。α₁受体阻断药哌唑嗪(1 μmol·L^-1)对2～8 Hz电刺激诱发的血管收缩反应无影响。P2X₁受体激动药α,β-亚甲基ATP(3 μmol·L^-1)脱敏P2X₁受体，同时联合应用哌唑嗪(1 μmol·L^-1)完全抑制电刺激诱发的血管收缩反应。采用一个标本一个浓度给药时，ISMN(0.1 mmol·L^-1)显著抑制8 Hz电刺激诱发的血管收缩反应，在0.3及1.0 mmol·L^-1时ISMN显著抑制各频率电刺激诱发的血管收缩反应； 1.0 mmol·L^-1 ISMN对电刺激诱发的血管收缩反应的抑制率分别为46%(2 Hz)、 47%(4 Hz)、 34%(8 Hz)和22%(16 Hz)。ISMN(0.3及1.0 mmol·L^-1)对外源性去甲肾上腺素(0.01～100 μmol·L^-1)或腺苷三磷酸(1 mmol·L^-1)诱发的血管收缩反应无影响。以上结果提示，ISMN显著抑制电场刺激诱发的交感嘌呤能血管收缩反应，其作用机制可能是ISMN作用于交感神经末梢突触前膜抑制嘌呤能神经递质产生的血管收缩反应。     

环维黄杨星D抗心房纤颤的作用及其电生理机制

环维黄杨星D(CVB-D)对CaCl₂-Ach诱发小鼠在体心房纤颤和乌头碱、哇巴因或肾上腺素所致豚鼠离体心房纤颤,有明显的剂量依赖性抑制作用,且作用强度与胺碘酮(Ami)相似。CVB-D0.3～100μmol·L^-1降低离体右心房自律性。对离体左心房,CVB-D0.3μmol·L^-1抑制肾上腺素引起的异常自律性,延长有效不应期和动作电位时程,降低兴奋性;高浓度时,可降低V_max,延长冲动传导时间。Ami0.3～30μmol·L^-1有相似的电生理作用,但对V_max无明显的影响。提示CVB-D可试用于心房纤颤的患者。     

Effects of the Anemonia sulcata Toxin (ATX II) on Intracellular Sodium and Contractility in Rat and Guinea-Pig Myocardium

Abstract: The effects of the Anemonia sulcata toxin ATX II on action potentials and contractility of isolated papillary muscles and single myocytes from rat and guinea-pig hearts have been studied. ATX II prolonged the action potential in both rat and guinea-pig papillary muscle. Although it produced a positive inotropic effect in guinea-pig papillary muscle, it failed to do so in rat papillary muscle. However, in single rat and guinea-pig ventricular cells, it both prolonged the action potential and had a positive inotropic effect. We suggest that ATX II does not cause a positive inotropic effect in rat papillary muscle, because it induces Ca²⁺ overload. In single cells the positive inotropic effect was reduced by ?50% when the contractions were triggered by voltage clamp pulses of constant duration rather than by action potentials. This suggests that the inotropic effect of ATX II is in part the result of the prolongation of the action potential. The intracellular Na⁺ activity (aⁱ_Na) in single ventricular cells was measured with the Na⁺-sensitive fluorescent dye SBFI. After exposure of the cells to ATX II, aⁱ_Na was increased by a maximum of 1.9 ± 0.3 and 2.2 ± 0.3 mM in rat and guinea-pig cells, respectively. It is suggested that the positive inotropic effect of ATX II is also in part the result of the rise in aⁱ_Na.     

3,4-二羟基苯乙酮(DHAP)对离体心肌电活动和机械活动的作用

The effects of DHAP on electrical and mechanical activities were investigated by synchronously recording action potential and isometric tension in isolated myocardium. No influence was demonstrated on action potential (APA, APD₂₀、APD₉₀) by DHAP 10^-5～10^-3M in guinea pig palillary muscle. The inhibition on the force of contraction with the same concentration of DHAP, however, was shown in a concentration-dependent way. The effects of DHAP on the electrical and mechanical activities in cat papillary muscle were similar to those in guinea pig papillary muscle. With the dose of DHAP 10^-5～5×10^-4M, alteration of action potential of pacemaker cells was not observed in the isolated sinus node preparation of the rabbit. When the dosage was increased to 10^-3 M, the electrical activities were inhibited. The experimental results indicate that the effects of a certain dose of DHAP on inhibiting the tension in myocardium are available in clinical application. A warning is given that an increase in dosage may enhance the inhibition on contractile force in myocardium and inhibit the automaticity of sinus node pacemaker cells.     

In vitro Evaluation of Acute Effects of Mitoxantrone (Novantrone®) in Rat and Guinea Pig Atria

Abstract: Since guinea pig and rat atria have been used as models to study acute anthracycline-induced cardiotoxicity, experiments were carried out in these preparations to evaluate possible acute cardiac effects mediated by mitoxantrone (MTX). After a latency period of approximately 90 min, MTX (10^-5—10^-4 M) promoted a concentration-related and time-dependent decrease of spontaneous rate in guinea pig atria. A similar but less intense effect after a longer latency interval was observed in rat atria. In this preparation, MTX (10^-5—10^-4 M) incubated up to 150 min., induced a gradual competitive β-adrenergic blocking effect on the positive chronotropic action of isoproterenol. This was characterized by a progressive decline of pD₂ values without altering E_max. A similar and stronger effect was found in isolated guinea pig atria incubated under same conditions with MTX, except that 10^-4 M exposed for 150 min. was able to depress the E_max to isoproterenol by 21.2%. In addition, MTX (10^-4 M) in this model promoted a non-competitive antagonistic effect on the chonotropic action of histamine. These data are compatible with the idea that MTX could induce cardiac acute effects qualitatively similar to but of lower potency than those produced by doxorubicin in these two models. In addition, guinea pig atria seemed to display higher sensitivity to MTX compared to rat atrial preparations.     

DPI 201-106, a novel cardioactive agent. Combination of cAMP-independent positive inotropic,negative chronotropic,action potential prolonging and coronary dilatory properties

Summary The in vitro cardiac effects of DPI 201-106, a novel piperazinyl-indole, were investigated.DPI 201-106 produced concentration-dependent positive inotropic effects in guinea-pig and rat left atria, kitten, rabbit and guinea-pig papillary muscles and Langendorff perfused hearts of rabbits between 10^–7 and 3×10^–6 mol/l. During isometric twitches, contraction and relaxation phases were prolonged in guinea-pig left atria and right ventricular papillary muscles from kitten and guinea-pigs. Spontaneous sinus rate was decreased in right atria of guinea-pigs and rats. Coronary flow increased in rabbit isolated hearts. Functional refractory period was increased in left atria from guinea-pigs and rats with EC₅₀ values of 1.7 and 0.24 mol/l respectively.In electrophysiological measurements, DPI 201-106 prolonged the action potential duration (APD₇₀) in guinea-pig papillary muscles up to 70% and in rabbit atria up to 120% at 3 mol/l. Other action potential characteristics were not changed in guinea-pig papillary muscles but V _max was decreased in rabbit left atria. The electrophysiological as well as the positive inotropic effects were stereoselective with the activity residing in the S-enantiomer.DPI 201-106 increased the Ca²⁺-sensitivity of skinned fibres from porcine trabecular septomarginalis with an EC₅₀ of 0.2 nmol/l. DPI 201-106 did not change cAMP levels in guinea-pig atria and rabbit papillary muscles. Slow action potentials were not induced by DPI 201-106 in partially depolarized guinea-pig papillary muscles. Phosphodiesterase activity of rat hearts was not inhibited by DPI 201-106 at pharmacologically relevant concentrations. The presence of propranolol did not influence the inotropic potency of DPI 201-106 in guinea-pig atria.In conclusion, DPI 201-106 represents a novel type of positive inotropic agents with a synergistic sarcolemmal and intracellular mechanism of action.     

速激肽受体拮抗剂对白三烯C4引起的豚鼠心血管反应的抑制作用

iv白三烯C₄(LTC₄)0.8nmol·kg^-1引起麻醉豚鼠血压降低和心脏微血管依文思蓝渗出增加。速激肽NK-1受体拮抗剂CP-96345 (2.06μmol·kg^-1,iv)和NK-2受体拮抗剂SR-48968(1.66μmol·kg^-1,iv)部分抑制心房微血管渗漏(分别为46.6%和37.5%);两药合用可明显抑制LTC₄引起的低血压和心房、心室微血管渗漏(分别为58.1%和54.1%),其作用与白三烯特异性拮抗剂ONO-1078(0.06μmol·kg^-1,iv)相似。结果表明速激肽NK-1和NK-2受体可能参与白三烯引起的低血压和心脏炎症反应。     

GABA and Glutamate Receptors as Therapeutic Targets in Neurodegenerative Disorders*

Abstract: The amiloride derivatives, 2′,3′-benzobenzamil (BB), 3′,4′-dichlorobenzamil (DCB), and 5-(N-4-chlorobenzyl)-2′,4′-dimethylbenzamil (CBDB) are known as inhibitors of the Na⁺/Ca²⁺ exchange. This kind of drug action was recently suggested to be a new inotropic mechanism. In guinea-pig myocardium, we have studied the inotropic and the accompanying electrophysiological effects of the three compounds in order to assess their selectivity of action. In left atria and in papillary muscle, force of contraction increased with DCB and CBDB (atria only) at a high concentration (5 × 10^-5 ? 10^-4 mol/l) and after long exposure time, whereas BB produced a negative inotropic effect. In the isolated perfused Langendorff heart, the amiloride derivatives tested decreased spontaneous heart rate and force of contraction and prolonged the duration of contraction. In isolated cardiac myocytes, sodium current, calcium current and the delayed rectifier were reduced by concentrations of BB, DCB and CBDB similar to the IC₅₀ values reported for the inhibition of the Na⁺/Ca²⁺ exchange. Our results demonstrate that the amiloride derivatives have multiple sites of action. It is concluded that more specific modulators of the Na⁺/Ca²⁺ exchange are required in order to define their contribution to the regulation of contractile activation of the heart.     

Removal of inactivation and blockade of cardiac Na+ channels by DPI 201-106 different voltage-dependencies of the drug actions

Summary The influence of the novel cardiotonic diphenylpiperazinylindole derivative. the racemic DPI 201-106. on cardiac Na⁺ channels was studied in conventional microelectrode experiments on papillary muscles of guinea pigs and in patch clamp experiments using inside-out patches excised from cultured neonatal rat cardiocytes. The maximal rate of rise (V _max) of Na⁺-dependent action potentials was taken as an estimate for INa. Racemic DPI (3 × 10^–6 mol/1) exerts a dual effect as it removes channel inactivation and may also block cardiac Na⁺ channels. Both drug actions proved highly voltage-dependent but a given change in membrane potential had a strictly different modulating influence on the two effects. The \0V _max depression induced by racemic DPI became attenuated due to hyperpolarization and finally tended to disappear at about -90 mV. while at the same time I _Na modification became increasingly accentuated. An increase in holding potential caused the non-decaying portion of the macroscopic I _Na to increase significantly. Resting inactivation remained operative in non-inactivating cardiac Na⁺ channels and showed a similar voltage-dependence as in normal Na⁺ channels. The differential voltage-dependencies of both DPI effects strongly suggest the existence of two binding sites for DPI.This work was supported by a grant of the Deutsche Forschungsgemeinschaft (Ko 778/2-1). Bonn, Federal Republic of Germany Send offprint requests to M. Kohlhardt at the above address     

The Isolated Mouse Atria as a New Model for Testing Cardioactive Drugs with Special Reference to Doxorubicin (Adriamycin®)

Spontaneously beating isolated atria from mice were used as a new in vitro model to characterize the mechanism of the cardiotoxic action of the anthracycline cytostatic doxorubicin (Adriamycin®). After stabilization at 28° the atria showed a contractile rate and – force of 284±31 (S.D.) beats/min. and 49±6.5 mg. Doxorubicin (Dox) (10^-6-10^-5 M) had a positive chronotropic action per se and decreased the pD₂ for the chronotropic action of isoprenaline in a dose-dependent way. However only the effect of the higher concentration proved statistically significant, a concentration which also caused a marked decrease (63%) of the E_max. Pretreatment with Dox 15 mg/kg intraperitoneally 72 hr previously did not influence the pD₂ but caused a significant increase in the E_max of the isoprenaline concentration response curve. The results indicate that Dox in vitro interferes with the β-adrenoceptor function of isolated mouse atria in an unspecific way and that the subacute cardiotoxicity of Dox in mice is probably not due to interference with the β-adrenoceptor system. Further it is concluded that isolated atria from mice may be a useful model for testing cardioactive drugs.     

Effects of lisinopril on cardiac contractility and ionic currents

1. The effects of lisinopril, an angiotensin-converting enzyme inhibitor, were studied on cardiac contractile force, action potential characteristics and membrane ionic currents.2. In guinea-pig atria, lisinopril (0.001–1 μM) exerted a negative inotropic effect which was accompanied by a shortening of the time to peak tension and time for total contraction. However, it did not modify atrial rate or the characteristics of the ventricular action potentials recorded either in normally polarized or in depolarized papillary muscles.3. In isolated guinea-pig ventricular myocytes, lisinopril had no effect on the inward L-type Ca²⁺ (I_Ca,L), the inward rectifier (I_K1) or the delayed rectifier K⁺ currents (I_K), but abolished the stimulation-dependent facilitation of the I_Ca,L. Furthermore, it did not alter a cloned human cardiac K⁺ current (hKv1.5) expressed in a mouse L cell line (Ltk⁻).4. The absence of negative inotropic effects in patients with congestive heart failure can be explained by the potent arterial vasodilator action of lisinopril which reduced left ventricular afterload overriding the expected direct cardiodepressant effects of the drug.