丹参酮Ⅱ—A磺酸钠对分离的豚鼠心室肌单细胞慢反应...

The sodium channels of dissociated single ventricular cells of adult guinea pig heart were inactivated by partial depolarization in high K+ (25 mmol/L) Tyrode's solution and slow response action potential was elicited by intracellular stimulation. An obvious inhibition of the response was observed in the presence of 20 mumol/L sodium tanshinone II-A sulfonate (DS-201). In the concentration range from 1 mumol/L to 20 mumol/L, the inhibition effect of sodium tanshinone II-A sulfonate on the slow response action potentials enhanced by 0.28 mumol/L isoprenaline is concentration-dependent. Moreover, the inhibition effects of sodium tanshinone II-A sulfonate become stronger with the increase (in the range of 6.9 nmol/L to 0.55 mumol/L) of isoprenaline. The above-mentioned results suggest that sodium tanshinone II-A sulfonate may be a kind of effective calcium channel blocker. Under the effect of high concentration (50-100 mumol/L) of sodium tanshinone II-A sulfonate, the amplitude of fast response action potential of dissociated ventricular myocytes of adult guinea pig was decreased and the time to reach the peak was prolonged. All these results indicate that sodium channels were blocked to a certain extent by the high concentration of sodium tanshinone II-A sulfonate.     

Wavelength dependence of the optically recorded action potentials in guinea pig atrial muscles.

The optically recorded action potentials of the frog atrial muscles which lack transverse tubules showed different features from those reported by Heiny and Vergara (Heiny JA, Vergara J. Optical signals from surface and T system membranes in skeletal muscle fibers. J Gen Physiol 1982;80:203-230) in skeletal muscles (Fujishiro N, Kawata H. The wavelength dependence of optically recorded action potentials in the atrial muscles of the bullfrog (Rana catesbeiana). Comp Biochem Physiol 1996;114A:153-157). We examined whether or not the differences were consistent in other atrial muscles which lack transverse tubules with guinea pig atrial muscles. Two dyes (merocyanine rhodanine and merocyanine oxazolone) were used, and the dependence of the maximum rising phase of the optical signals on the wavelength of the incident beam was analyzed. No dependence was observed between them, and this finding was consistent with the structure of the membrane system of the guinea pig atrial muscles. The optical signals recorded at 718 nm of the incident beam from the guinea pig atrial muscles which stained with merocyanine oxazolone showed a more prominent second rising phase after the initial rapid rising phase of the optical signal than that recorded in the frog atrial muscles. This phase was not observed in the optical signals recorded at other wavelengths. The features of the optically recorded action potentials in guinea pig atrial muscles were consistent with those recorded in frog atrial muscles. Nifedipine did not affect the second rising phase.     

Genistein对豚鼠右心室肌收缩功能的影响

目的:观察genistein(GEN)对离体豚鼠右心室肌收缩功能的影响,并探讨其作用机理。方法:将离体豚鼠右心室肌置于装有K-H液的灌流肌槽中,待平衡后,加入各种药物观察心室肌收缩活动的变化。结果:GEN和异丙肾上腺素相似,可增强右心室肌的收缩活动,GEN(1～100μmol·L-1)的作用还具有明显的剂量依赖性。心得安(1μmol·L-1)和异搏定(0.5μmol·L-1)虽可明显阻断异丙肾上腺素(1μmol·L-1)的正性肌力作用,但对GEN(50μmol·L-1)的心肌收缩增强效应无明显改变;同时发现GEN(1,10μmol·L-1)温育后,对细胞外液Ca2 浓度升高而诱发的心肌收缩力增强也无明显影响。另外,它莫西芬(1μmol·L-1)及SQ22536(1μmol·L-1)可减弱GEN的正性肌力作用,bpV(1μmol·L-1)也可部分阻断GEN的这种作用。结论:GEN可增强右心室肌的收缩活动,其作用与心肌细胞膜上的β肾上腺素能受体、钙通道的激活无关,可能与cAMP的胞内信号转导以及酪氨酸激酶途径有一定关系。     

Aberrant cell-to-cell coupling in Ca2+-overloaded guinea pig ventricular muscles

To investigate how intercellular coupling can be changed during Ca²⁺ overloading of ventricular muscle, we studied Ca²⁺ signals in individual cells and the histochemistry of the major gap junction channel, connexin43 (Cx43), using multicellular preparations. Papillary muscles were obtained from guinea pig ventricles and loaded with rhod-2. Sequential Ca²⁺ images of surface cells were obtained with a confocal microscope. In intact muscles, all cells showed simultaneous Ca²⁺ transients in response to field stimulation over a field of view of 0.3 x 0.3 mm². In severely Ca²⁺-overloaded muscles, obtained by high-frequency stimulation in nonflowing Krebs solution, cells became less responsive to stimulation. Furthermore, nonsimultaneous but serial onsets of Ca²⁺ transients were often detected, suggesting a propagation delay of action potentials. The time lag of the onset between two aligned cells was sometimes as long as 100 ms. Similar lags were also observed in muscles with gap junction channels inhibited by heptanol. To investigate whether the phosphorylation state of Cx43 is affected in Ca²⁺-overloaded muscles, the distributions of phosphorylated and nonphosphorylated Cx43 were determined using specific antibodies. Most of the Cx43 was phosphorylated in the nonoverloaded muscles, whereas nonphosphorylated Cx43 was significantly elevated in severely Ca²⁺-overloaded muscles. Our results suggest that the propagation delay of action potential within a small area, a few square millimeters, can be a cause of abnormal conduction and a microreentry in Ca²⁺-overloaded heart. Inactivation of Na⁺ channels and inhibition of gap junctional communication may underlie the cell-to-cell propagation delay. Ca²⁺ transient; connexin43; propagation delay; gap junction; arrhythmia     

镉对豚鼠乳头肌动作电位的影响

目的:研究氯化镉(CdCl2)对正常豚鼠心室乳头肌细胞动作电位(AP)的影响。方法:用常规细胞内微电极方法记录乳头肌细胞AP。结果:在生理条件下,CdCl2可使APo期振幅(APA)和最大除极速率(Vmax)降低,动作电位时程(APD)缩短,且具有剂量依赖性。结论:CdCl2可使心室肌AP的APA、Vmax、APD发生改变,提示CdCl2有抑制Na 、Ca2 内流和激活K 外流作用。     

铃蟾肽介导的豚鼠肠系膜下神经节非胆碱能迟慢兴奋性突触后电位

应用细胞内记录技术,对铃蟾肽(bombesin,BOM)在豚鼠离体肠系膜下神经节(inferior mesenteric ganglion,IMG)非胆碱能兴奋性突触传递中的作用进行了研究。重复电刺激突触前结肠神经,有74．3％(52／70)IMG细胞可诱发迟慢兴奋性突触后电位(ls-EPSP)。在可引出ls-EPSP的细胞中,22％(4／18)细胞同时对BOM和SP敏感。用BOM持续灌流IMG,可明显抑制对BOM敏感细胞的ls-EPSP,对BOM不敏感细胞的ls-EPSP则无影响,且BOM受体与SP受体间无交叉脱敏。BOM受体阻断剂tyr^4[D-phe^12]bombesin能明显可逆性地抑制BOM敏感细胞的ls-EPSP和去极化,但对BOM不敏感细胞则无影响。研究结果提示,BOM可能是介导豚鼠IMG细胞ls-EPSP的一种递质。     

The sodium current underlying action potentials in guinea pig hippocampal CA1 neurons

Neurons were acutely dissociated from the CA1 region of hippocampal slices from guinea pigs. Whole-cell recording techniques were used to record and control membrane potential. When the electrode contained KF, the average resting potential was about -40 mV and action potentials in cells at -80 mV (current-clamped) had an amplitude greater than 100 mV. Cells were voltage-clamped at 22-24 degrees C with electrodes containing CsF. Inward currents generated with depolarizing voltage pulses reversed close to the sodium equilibrium potential and could be completely blocked with tetrodotoxin (1 microM). The amplitude of these sodium currents was maximal at about -20 mV and the amplitude of the tail currents was linear with potential, which indicates that the channels were ohmic. The sodium conductance increased with depolarization in a range from -60 to 0 mV with an average half-maximum at about -40 mV. The decay of the currents was not exponential at potentials more positive than -20 mV. The time to peak and half-decay time of the currents varied with potential and temperature. Half of the channels were inactivated at a potential of -75 mV and inactivation was essentially complete at -40 to -30 mV. Recovery from inactivation was not exponential and the rate varied with potential. At lower temperatures, the amplitude of sodium currents decreased, their time course became longer, and half-maximal inactivation shifted to more negative potentials. In a small fraction of cells studied, sodium currents were much more rapid but the voltage dependence of activation and inactivation was very similar.     

Hypothermic effects on action potential and force production of hedgehog and guinea pig papillary muscles

Action potentials and isometric force were recorded in papillary muscles from guinea pigs and summer hedgehogs at different temperatures between 37 and 0 degrees C. The action potential of the hedgehog was of a lower amplitude (mean 83 +/- 6 mV) than that of the guinea pig (mean 110 +/- 5 mV). The action potential duration at 50% repolarization was 22 +/- 2 msec in the hedgehog as compared to 105 +/- 11 msec in the guinea pig. Moreover, there was no distinct plateau phase of the hedgehog action potential. Lowering temperature prolonged the action potential duration in the two preparations by about the same percentage. However, the guinea pig preparation became progressively less excitable below 20 degrees C. Lowered temperature produced a positive inotropic effect in the guinea pig, whereas this effect was very slight in the hedgehog heart. Postextrasystolic potentiation was seen in the guinea pig but not in the hedgehog preparation. It is suggested that this difference between the preparations may be due to a greater relative amount of activator calcium in the hedgehog heart. The difference in cold tolerance between the preparations may reflect a difference in chemical composition of the sarcolemma.     

Ca-dependent slow action potentials in neuromuscular diseases

Slow Ca-dependent action potentials were studied in skeletal muscle fibers from different Neuromuscular Diseases (NMD). Biopsies were obtained from: 3 myopathies [Fascioscapulohumeral Dystrophy (FSH) and Polymyositis (PM)], 6 patients with other diseases (CD) [Amyotrophic Lateral Sclerosis (ALS), Central Core Disease, Mitochondrial Myopathy, Polyneuritis (PN), von Eulenberg's Paramyotonia], and 8 normal control muscles. Experiments were carried out in muscle fibers under current-clamp conditions. Membrane currents other than Ca ones were abolished or greatly diminished. Muscle fibers produced any of 3 types of responses, when stimulated by depolarizing pulses: fully developed Ca-action potentials (CaAP), abortive non-regenerative Ca responses (NrR), or only capacitive passive responses (WR). The 3 types of responses were not dependent on the basal conditions of the fibers. The frequency of observation of CaAPs was significantly higher in myopathic disease. In myopathies, 46% of the muscle fibers had CaAPs, while only 22% of fibers from CD and 15% of the fibers from normal muscles showed CaAPs. No differences were observed in the resting constants as well as in the CaAPs parameters between normal and diseased muscle fibers.     

白藜芦醇对离体豚鼠乳头状肌的电生理效应

本文旨在应用标准玻璃微电极技术,观察白藜芦醇对离体豚鼠乳头状肌的电生理效应。结果显示：(1)白藜芦醇(30、60、120μmol／L)可剂量依赖性地缩短乳头状肌细胞的动作电位时程;(2)对部分去极化的乳头状肌,白藜芦醇(60μmol／L)不仅缩短动作电位时程,而且降低动作电位的幅值和超射值,减慢零期最大上升速度;(3)用无钙K-H液灌流标本可完全取消白藜芦醇对乳头状肌细胞的作用：(4)钾通道开放剂四乙基氯化铵(TEA,20mmol／L),不能阻断白藜芦醇的电生理效应;(5)预先应用一氧化氮合酶抑制剂L-NAME(1mmol／L),对白藜芦醇的上述效应无影响。以上结果表明,白藜芦醇可缩短正常乳头状肌细胞动作电位时程,这一效应可能与其抑制钙离子内流有关,但此作用机制中NO的作用并不显著。     

Electrical rhythmicity and spread of action potentials in longitudinal muscle of guinea pig distal colon

Using simultaneous intracellular recordings, we have characterized 1) electrical activity in the longitudinal muscle (LM) of isolated segments of guinea pig distal colon free to contract spontaneously and 2) extent of propagation of spontaneous action potentials around the circumference of the colon. In all animals, rhythmical spontaneous depolarizations (SDs) were recorded that are usually associated with the generation of action potentials. Recordings from pairs of LM cells, separated by 100 microm in the circumferential axis, revealed that each action potential was phase locked at the two electrodes (mean propagation velocity: 3 mm/s). However, at an increased electrode separation distance of 1 mm circumferentially, action potentials and SDs became increasingly uncoordinated at the two recording sites. No SDs or action potentials ever propagated from one circumferential edge to the other (i.e., 13 mm apart). When LM strips were separated from the myenteric plexus and circular muscle, rhythmically firing SDs and action potentials were still recorded. Atropine (1 microM) or tetrodotoxin (1 microM) either reduced the frequency of SDs or temporarily abolished activity, whereas nifedipine (1 microM) always abolished SDs and action potentials. Kit-positive interstitial cells of Cajal were present at the level of the myenteric plexus and circular and longitudinal muscle. In summary, SDs and action potentials in LM propagate over discrete localized zones, usually <1 mm around the circumference of the colon. Furthermore, in contrast to the classic slow wave, rhythmic depolarizations in LM appear to be generated by an intrinsic property of the smooth muscle itself and are critically dependent on opening of L-type Ca(2+) channels.     

豚鼠主动脉前庭自发性慢反应电位去极离子流的初步分析

为研究主动脉前庭自发慢反应电位的去极离充性质,利用豚鼠的离体以及心脏,常规玻璃微电极细胞内记录方法和离子通道组断剂,观测最大舒张电位（ＭＤＰ）、０相除极幅度（ＡＰＡ）、０相最大除极速度（Ｖｍａｘ）、４个自动除极速度（ＶＤＤ）、复极５０％（ＡＰＤ５０）和９０％（ＡＰＤ９０）的时间以及自发放电频率（ＲＰＦ）。结果发现：⑴０．５μｍｏｌ／Ｌ尼索地平（Ｎｉｓ）可使该慢电位的ＡＰＡ、Ｖｍａｘ、ＶＤＤ明显减小     

Fast-white and fast-red isomyosins in guinea pig muscles

Myosins isolated from guinea pig fast-white Tensor Fasciae Latae (TFL) and fast-red Masseter (MASS) muscles displayed similar light chains pattern as revealed by two-dimen-sional gel electrophoresis. In contrast, the heavy chain stru$\text{c}$ ture was found to be different as shown by electrophoretic peptide maps obtained by treating myosins with different proteases.     

辣椒素对离体豚鼠乳头状肌的电生理效应

应用细胞内微电极技术,观察了辣椒素(capsaicin,CAP)对豚鼠乳头状肌细胞的电生理效应。结果表明：(1)CAP(30、60、120μmol／L)可浓度依赖地缩短正常乳头状肌的动作电位时程。(2)对部分去极化乳头状肌,CAP(60μmol／L)除缩短动作电位时程外,还使动作电位幅值和超射值降低,零相最大上升速度减慢。(3)预先应用L型钙通道开放剂Bay K8644(0．5μmol／L),则可阻断CAP(60μmol／L)的电生理效应。(4)预先应用辣椒素受体(va-nilloid receptor,VR)阻断剂钌红(20μmol／L),不影响CAP(60μnol／L)的电生理效应。以上结果提示,CAP可能通过非受体途径抑制Ca^2 内流,从而影响豚鼠乳头状肌电生理效应。     

Mechanism of hypoxic preconditionin in guinea pig papillary muscles

Brief ischemia or hypoxia has been found to protect the heart against susbsequent long-lasting ischemia and to improve contractile dysfunction as well to reduce cell necrosis and the incidence of lethal arrhythmias. This phenomenon, termed preconditioning (PC) has been demonstrated in different species. However, little is known about PC in guinea pigs. Moreover, electrophysiological changes underlying protection have not been studied so far in conjuntion with force recovery in a setting of PC. The aim of the study was to study PC in a guinea pig papillary muscle, using recovery of contractility after long hypoxic challenge as the main end-point of protection, and to investigate concominant electrophysiological alterations. In guinea pig papillary muscle preparations contracting isometrically (paced at 2 Hz), transmembrane action potentials (AP) and developed force (DF) were recorded by conventional microelectrode technique and a force tranducer. In addition, effective refractory periods (ERP) were determined. Hypoxia was induced by superfusion with 100% N₂ (pO₂ < 5 kPa) and pacing at 3,3 Hz. In the control group, long hypoxia lasted for 45 min and was followed by 30 min reoxygenation. In the PC group, muscles were subjected to 5 min hypoxia followed by 10 min recovery prior to sustained hypoxia/reoxygenation. Results: Long hypoxia induced a similar depression of DF in both, PC and control groups. However, a loss of contractile activity occured earlier in the PC group. AP duration and ERP decreased faster and were significantly shorter after PC. Upon reoxygenation, preconditioned muscles showed significantly better recovery of function (DF 86% of prehypoxic value vs. 36% in controls; p < 0,05). AP and ERP were completely restored in both, PC and control groups. Guinea pig papillary muscle can be preconditioned with a brief hypoxic challenge against contractile dysfunction upon long-lasting hypoxia/reoxygenation. Shortening of AP and loss of contractility occured more quickly during hypoxia and may participate in the protective effect of preconditioning. Possible mechanisms might involve facilitated opening of K_ATP-dependent channels.     

Ca-dependent slow action potentials in human skeletal muscle

Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained during surgery (fibers with both ends cut). Control studies also were carried out with intact as well as cut rat skeletal muscle fibers. Experiments were performed in hypertonic Cl-free saline with 10 or 84 mM Ca and K-channel blockers; muscles were preincubated in a saline containing Cs and tetraethylammonium. A current-clamp technique with two intracellular microelectrodes was used. In human muscle, 14.5% of the fibers showed fully developed CaAPs, 21% displayed nonregenerative Ca responses, and 64.5% showed only passive responses; CaAPs were never observed in 10 mM Ca. In rat muscle, nearly 90% of the fibers showed CaAPs, which were not affected by the cut-end condition. Human and rat muscle fibers had similar membrane potential and conductance in the resting state. In human muscle (22-32 degrees C, 84 mM Ca), the threshold and peak potential during a CaAP were +26 +/- 6 mV and +70 +/- 3 mV, respectively, and the duration measured at threshold level was 1.7 +/- 0.5 sec. In rat muscle, the duration was four times longer. During a CaAP, membrane conductance was assumed to be a leak conductance in parallel with a Ca and a K conductance. In human muscle (22-32 degrees C, 84 mM Ca, 40 micron fiber diameter), values were 0.4 +/- 0.1 microS, 1.1 +/- 0.7 microS, and 0.9 +/- 0.4 microS, respectively. Rat muscle (22-24 degrees C, 84 mM Ca) showed leak and K conductances similar to those found in human fibers. Ca-conductance in rat muscle was double the values obtained in human muscle fibers.     

Effects of Na+/Ca2+ exchange induced by SR Ca2+ release on action potentials and afterdepolarizations in guinea pig ventricular myocytes

In cardiac cells, evoked Ca2+ releases or spontaneous Ca2+ waves activate the inward Na+/Ca2+ exchange current (INaCa), which may modulate membrane excitability and arrhythmogenesis. In this study, we examined changes in membrane potential due to INaCa elicited by sarcoplasmic reticulum (SR) Ca2+ release in guinea pig ventricular myocytes using whole cell current clamp, fluorescence, and confocal microscopy. Inhibition of INaCa by Na+-free, Li+-containing Tyrode solution reversibly abbreviated the action potential duration at 90% repolarization (APD90) by 50% and caused SR Ca2+ overload. APD90 was similarly abbreviated in myocytes exposed to the Na+/Ca2+ exchange inhibitor KB-R7943 (5 microM) or after inhibition of SR Ca2+ release with ryanodine (20 microM). In the absence of extracellular Na+, spontaneous SR Ca2+ releases caused minimal changes in resting membrane potential. After the myocytes were returned to Na+-containing solution, the potentiated intracellular Ca2+ concentration ([Ca2+]i) transients dramatically prolonged APD90 and [Ca2+]i oscillations caused delayed and early afterdepolarizations (DADs and EADs). Laser-flash photolysis of caged Ca2+ mimicked the effects of spontaneous [Ca2+]i oscillations, confirming that APD prolongation, DADs, and EADs could be ascribed to intracellular Ca2+ release. These results suggest that Na+/Ca2+ exchange is a major physiological determinant of APD and that INaCa activation by spontaneous SR Ca2+ release/oscillations, depending on the timing, can account for both DADs and EADs during SR Ca2+ overload.     

胍基丁胺在离体豚鼠乳头肌的电生理效应

应用细胞内微电极技术,观察了胍基丁胺（ａｇｍａｔｉｎｅ,ＡＧＭ）对豚鼠乳头肌细胞的电生理效应。结果表明：（１）ＡＧＭ浓度依赖地缩短正常乳头肌动作电位的时程;（２）对部分去极化的乳头肌,ＡＧＭ（１ｍｍｏｌ／Ｌ）除缩短动作电位时程外,还抑制动作电位零相最大上升速度,并降低其幅值和超射值;（３）预先应用一氧化氮合酶抑制剂ＬＮＡＭＥ（０５ｍｍｏｌ／Ｌ）,不能影响ＡＧＭ（１ｍｍｏｌ／Ｌ）的电生理效应;（４）预先应用咪唑啉受体（ｉｍｉｄａｚｏｌｉｎｅｒｅｃｅｐｔｏｒ,ＩＲ）和α２肾上腺素能受体（ａｌｐｈａ２ａｄｒｅｎｅｒｇｉｃｒｅｃｅｐｔｏｒ,α２ＡＲ）拮抗剂ｉｄａｚｏｘａｎ（０１ｍｍｏｌ／Ｌ）,则可完全阻断ＡＧＭ（１ｍｍｏｌ／Ｌ）的电生理效应。以上结果提示,ＡＧＭ对乳头肌的电生理效应似由α２ＡＲ和ＩＲ介导,并与胞浆内Ｃａ２＋减少有关。