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High intracellular [Ca²⁺] alters sarcoplasmic reticulum function in skinned skeletal muscle fibres of the rat

JOURNAL OF PHYSIOLOGY-LONDON 1999年第3期519卷 815-827页

作者： Lamb, GD Cellini, MA La Trobe Univ Dept Zool Bundoora Vic 3083 Australia

1. The effect on sarcoplasmic reticulum (SR) function of exposure to high intracellular [Ca2+]. was studied in mechanically skinned fibres from the extensor digitorum longus muscle of the rat, using caffeine to assay the SR Ca2+ content. 2. A 15 s exposure to 50 mu M Ca2+ irreversibly reduced the ability of the SR to load/retain Ca2+ and completely abolished depolarization-induced Ca2+ release, whereas a 90 s exposure to 10 mu M Ca2+ had no detectable effect on either function. The reduction in net SR Ca2+ uptake: (a) was near-maximal with treatment at 50 mu M Ca2+, (b) was unrelated to voltage-sensor function, and (c) persisted unchanged for > 20 min. The reduction was primarily due to a threefold increase in leakage of Ca2+ out of the SR. This increased leakage was not substantially blocked by the presence of 10 mM Mg2+ or 2 mu M Ruthenium Red. 3. The adverse effect on SR function of exposure to high [Ca2+] could also be observed by the reduction in the ability of the SR to maintain a low [Ca2+] within the skinned fibre in the face of elevated [Ca2+] in the bathing solution. When bathed in a solution with similar to 1.5 mu M Ca2+ (0.75 mM CaEGTA-EGTA), skinned fibres produced only low force responses for many minutes, but after high [Ca2+] treatment (15 s exposure to 50 mu M Ca2+) they showed large, steady or oscillatory force responses. 4. These findings indicate that, in addition to uncoupling the Ca2+ release channels from the voltage sensors, exposure of skinned fibres to high [Ca2+] causes a persistent increase in resting Ca2+ efflux from the SR. Such efflux in an intact fibre would alter the distribution of Ca2+ between the SR, the cytoplasm and the extracellular solution. These results may be relevant to the basis of low-frequency fatigue and possibly other conditions in muscle.

关键词：咖啡因/药理学钙/代谢镁/药理学肌骨骼/药物作用肌骨骼/生理学钌红/药理学肌浆网/药物作用肌浆网/生理学动物大鼠

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CLINICAL SIGNS AND NATURAL-HISTORY OF ALCOHOLIC HEART-DISEASE

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ANNALS OF THE NEW YORK ACADEMY OF SCIENCES 1975年第APR25期252卷 264-272页

作者： GUNNAR, RM DEMAKIS, J RAHIMTOOLA, SH SINNO, MZ TOBIN, JR LOYOLA UNIV STRITCH SCH MED SECT CARDIOL MAYWOOD IL 60153 USA VET ADM HOSP SECT CARDIOL HINES IL 60141 USA UNIV OREGON MED SCH PORTLAND OR 97201 USA LOYOLA UNIV STRITCH SCH MED DEPT MED MAYWOOD IL 60153 USA

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CA-RELEASING ACTION OF BETA,GAMMA-METHYLENE ADENOSINE-TRIPHOSPHATE ON FRAGMENTED SARCOPLASMIC-RETICULUM

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JOURNAL OF BIOCHEMISTRY 1976年第5期80卷 1149-1157页

作者： OGAWA, Y EBASHI, S UNIV TOKYO FAC MED DEPT PHARMACOL BUNKYO KU TOKYO 113 JAPAN

.beta.,.gamma.-Methylene ATP (AMPOPCP) had 2 effects on fragmented [bullfrog] sarcoplasmic reticulum (FSR), i.e., inhibition of the rate of Ca uptake and the induction of Ca release from FSR filled with Ca. The Ca release brought about by AMPOPCP had many features in common with the mechanism of Ca-induced Ca release: it was inhibited by 10 mM procaine;the amount of Ca release increased with increase in the extent of saturation of FSR with Ca;increase of the Ca concentration in the medium facilitated the relase of Ca. However, no facilitation of Ca release upon decrease of Mg concentration in the medium was observed. AMPOPCP and caffine potentiated each other remarkably in their Ca-releasing action, irrespective of the kind of substrate. The state of the FSR-ATP complex was crucial for Ca-induced Ca release.

关键词：腺苷三磷酸/类似物和衍生物腺苷三磷酸/代谢咖啡因/药理学钙/代谢氨甲酰磷酸盐/药理学镁/代谢草酸盐类/药理学普鲁卡因/药理学肌浆网/药物作用肌浆网/代谢锶/代谢

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Sarcoplasmic reticulum Ca²⁺ release by 4-chloro-m-cresol (4-CmC) in intact and chemically skinned ferret cardiac ventricular fibers

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JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS 1999年第2期290卷 578-586页

作者： Choisy, S Huchet-Cadiou, C Leoty, C Fac Sci & Tech Nantes Lab Physiol Gen CNRS EP 1593 F-44322 Nantes 3 France

The purpose of this study was to determine whether 4-chloro-m-cresol (4-CmC) could generate caffeine-like responses in ferret cardiac muscle. The concentration dependence of 4-CmC-mediated release of Ca2+ from the sarcoplasmic reticulum was studied in intact cardiac trabeculae and saponin-skinned fibers in which the sarcoplasmic reticulum was loaded with Ca2+. In intact and saponin-skinned preparations isolated from right ventricle, the effect of 4-CmC on sarcoplasmic reticulum Ca2+ content was estimated by analysis of caffeine contracture after application of chlorocresol. In addition, the effects of 4-CmC on maximal Ca2+-activated tension and the Ca2+ sensitivity of myofibrils were analyzed by using Triton-skinned cardiac fibers. The results show that 4-CmC generates a contractile response in saponin-skinned but not intact fibers. The sarcoplasmic reticulum is implicated in the 4-CmC response;more precisely, in Ca2+ release via the ryanodine receptor. Moreover, 4-CmC, like caffeine, has effects on maximal Ca2+-activated tension and the Ca2+ sensitivity of myofibrils.

关键词：咖啡因/药理学钙/代谢收缩蛋白质类/代谢甲酚类/药理学雪貂心室/药物作用心室/代谢心室/超微结构动力学肌纤维/药物作用肌纤维/代谢肌纤维/超微结构心肌收缩/药物作用心肌/细胞学心肌/代谢心肌/超微结构辛苯昔醇/药理学兰尼碱受体钙释放通道/药物作用兰尼碱受体钙释放通道/代谢皂苷类/药理学肌浆网/药物作用肌浆网/代谢动物男(雄)性

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EFFECTS OF TETRACAINE ON DISPLACEMENT CURRENTS AND CONTRACTION OF FROG SKELETAL-MUSCLE

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JOURNAL OF PHYSIOLOGY-LONDON 1976年第3期262卷 583-611页

作者： ALMERS, W BEST, PM UNIV WASHINGTON DEPT PHYSIOL & BIOPHYS SEATTLE WA 98195 USA PHYSIOL LAB CAMBRIDGE CB2 3EG ENGLAND

The kinetics of mechanical activation of intact [Rana temporaria] fibers were examined with a voltage-clamp technique. Tetracaine (2 mM) increased 15- to 70-fold the time required to produce a just visible contraction by cell membrane depolarization. Displacement currents thought to be related to contractile activation remained in 2 mM tetracaine. Their characteristics were virtually identical to those found in the absence of the drug. Displacement currents also remained in fibers immobilized by treatment with 10 mM formaldehyde. Despite its effect on contraction of intact fibers, tetracaine did not diminish contraction tension when Ca was applied directly to the contractile proteins of skinned muscle fibers. The sensitivity of the myofilaments to Ca2+ also remained undiminished. When acting on intact fibers the drug must have inhibited Ca2+ released from the sarcoplasmic reticulum. It was estimated that 2 mM tetracaine diminished more than 10-fold the capacity for Ca2+-release in response to cell membrane depolarization. If muscle displacement currents represented events linking depolarization to Ca2+-release, then tetracaine must have been able to block the release without affecting the potential-sensing portion of the release regulating mechanism. Further experiments on skinned fibers have shown that tetracaine blocked or greatly diminished caffeine contractions, but that Cl-induced contractions of normal amplitude were still possible.

关键词：钙/代谢钙/药理学细胞膜/药物作用氯化物/药理学甲醛/药理学动力学膜电位/药物作用肌收缩/药物作用肌/药物作用豹纹蛙林蛙肌浆网/药物作用丁卡因/药理学动物

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Effects of tetracaine on sarcoplasmic calcium release in mammalian skeletal muscle fibres

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JOURNAL OF PHYSIOLOGY-LONDON 1999年第3期515卷 843-857页

作者： Csernoch, L Szentesi, P Sárközi, S Szegedi, C Jona, I Kovács, L Debrecen Univ Med Sch Med Dept Physiol H-4012 Debrecen Hungary

*** muscle fibres were dissociated enzymatically from the extensor digitorum communis muscle of rats. The fibres were mounted into a double Vaseline gap experimental chamber and the events in excitation-contraction coupling were studied under voltage clamp conditions in the presence and absence of the local anaesthetic tetracaine. 2. Changes in intracellular calcium concentration ([Ca2+](i)) were monitored using the calcium sensitive dyes antipyrylazo III and fura-2 and the rate of calcium release (R-rel) from the sarcoplasmic reticulum (SR) was calculated Tetracaine decreased the maximal attained [Ca2+](i) and suppressed, in a dose-dependent manner, both the early peak and the steady level of R-rel in the voltage range examined. 3. The concentration dependence of the effects on the two kinetic components of R-rel were almost identical with a half-effective concentration (K-50) of 70 and 71 mu m and a Hill coefficient (n(H)) of 2.7 and 2.3 for the peak and the steady level, respectively Furthermore, the drug did not alter the peak to steady level ratio up to a concentration (50 mu M) that caused a 35 +/- 5% reduction in calcium release. Higher concentrations did suppress the ratio but the degree of suppression was voltage independent. 4. Tetracaine (50 mu M) neither influenced the total available intramembrane charge nor altered its membrane potential dependence. It shifted the transfer function, the normalized SR permeability versus normalized charge to the right, indicating that similar charge transfer caused a smaller increase in SR permeability. 5. To explore the site of action of tetracaine further the ryanodine receptor (RyR) calcium release channel of the SR was purified and reconstituted into planar lipid bilayers. The reconstituted channel had a conductance of 511 +/- 14 pS (n = 8) in symmetric 250 mM KCl that was not affected bq tetracaine. Tetracaine decreased the open probability of the channel in a concentration-dependent manner with K-50 = 68 mu M

关键词：钙/代谢依他酸/药理学动力学哺乳动物膜电位/药物作用膜电位/生理学肌骨骼/生理学兰尼碱受体钙释放通道/分离和提纯兰尼碱受体钙释放通道/生理学肌浆网/药物作用肌浆网/代谢丁卡因/药理学动物大鼠

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THE ENHANCEMENT OF CA2+ EFFLUX FROM SARCOPLASMIC-RETICULUM VESICLES BY UREA

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ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 1992年第1期299卷 73-76页

作者： CHINI, EN DEFARIA, FO CARDOSO, CM DEMEIS, L UNIV FED RIO DE JANEIRO INST CIENCIAS BIOMEDDEPT BIOQUIMCIDADE UNIVBR-21910 RIO JANEIROBRAZIL

Urea, in nondenaturing concentrations, inhibited Ca2+ uptake by sarcoplasmic reticulum vesicles with no concomitant effect on ATP hydrolysis. This inhibition was antagonized by 5 mM oxalate and 20 mM orthophosphate. At concentrations of 0.2 to 1.0 M, urea induced an increase in the Ca2+ efflux from preloaded vesicles diluted in a medium at pH 7.0 containing 2 mM ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid, 0.1 mM orthophosphate, and 0.1 mM MgCl2. The urea-induced efflux was arrested by ligands of the (Ca(2+)-Mg2+) ATPase, namely, K+, Mg2+, Ca2+, and ADP, and by ruthenium red and the polyamines spermine, spermidine, and putrescine. In the case of polyamines a dissociation between the effect on the efflux and the net Ca2+ uptake was observed, as only the efflux could be blocked by the drugs. Glycine betaine, trimethylamine-N-oxide, and sucrose antagonized the effects of urea on both the net Ca2+ uptake and the rate of Ca2+ efflux.

关键词：腺苷二磷酸/药理学甜菜碱/药理学钙/代谢动力学镁/药理学肌/代谢草酸盐类/药理学草酸磷酸盐类/药理学聚胺类/药理学钾/药理学钌红/药理学肌浆网/药物作用肌浆网/代谢尿素/拮抗剂和抑制剂尿素/药理学动物兔

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Interactions of 6-gingerol and ellagic acid with the cardiac sarcoplasmic reticulum Ca²⁺-ATPase

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JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS 1999年第1期290卷 227-234页

作者： Antipenko, AY Spielman, AI Kirchberger, MA CUNY Mt Sinai Sch Med Dept Phys & Biophys New York NY 10029 USA

The inotropic/lusitropic effects of p-adrenergic agonists on the heart are mediated largely by protein kinase A (PKA)-catalyzed phosphorylation of phospholamban, the natural protein regulator of the Ca2+ pump present in sarcoplasmic reticulum (SR) membranes. Gingerol, a plant derivative, is known to produce similar effects when tested in isolated cardiac muscle. The purpose of the present study was to compare the effects of gingerol and another plant derivative, ellagic acid, on the kinetics of the SR Ca2+ pump with those of PKA-catalyzed phospholamban phosphorylation to elucidate their mechanisms of Ca2+ pump regulation. As previously demonstrated for PKA, 50 mu M gingerol or ellagic acid increased V-max(Ca) of Ca2+ uptake and Ca2+-ATPase activity assayed at millimolar ATP concentrations in light cardiac SR vesicles. Unlike PKA, which decreases K-m(Ca), neither compound had a significant effect on K-m(Ca) in unphosphorylated vesicles. However, gingerol increased K-m(Ca) in phosphorylated vesicles, in which Ca2+ uptake was significantly increased further at saturating Ca2+ and remained unchanged at subsaturating Ca2+. An inhibition of Ca2+ uptake by gingerol at micromolar MgATP concentrations was overcome with increasing MgATP concentrations. The stimulation of Ca2+ uptake attributable to gingerol in unphosphorylated microsomes at saturating Ca2+ was 30% to 40% when assayed at 0.05 to 2 mM MgATP and only about 12% in phosphorylated microsomes as well as in rabbit fast skeletal muscle light SR. The present results support the view that an ATP-dependent increase in V-max(Ca) of the SR Ca2+ pump plays an important role in mediating cardiac contractile responses to gingerol and phospholamban-dependent beta-adrenergic stimulation.

关键词：钙/代谢钙转运ATP酶类/拮抗剂和抑制剂钙转运ATP酶类/代谢环AMP依赖性蛋白激酶类/代谢鞣花酸/药理学脂肪族醇类/药理学草药-药物相互作用动力学微粒体/药物作用微粒体/酶学肌骨骼/药物作用肌骨骼/酶学肌骨骼/超微结构心肌/酶学心肌/代谢心肌/超微结构磷酸盐类/代谢磷酰化植物药用肌浆网/药物作用肌浆网/酶学动物狗兔

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The role of the sarcoplasmic reticulum as a Ca²⁺ sink in rat uterine smooth muscle cells

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JOURNAL OF PHYSIOLOGY-LONDON 1999年第1期520卷 153-163页

作者： Shmigol, AV Eisner, DA Wray, S Univ Liverpool Physiol Lab Dept Physiol Liverpool L69 3BX Merseyside England Univ Liverpool Dept Vet Preclin Sci Liverpool L69 3BX Merseyside England

1. The mechanisms responsible for removing calcium ions from the cytoplasm were investigated in single rat uterine myocytes using indo-1. 2. Trains of depolarizing voltage-clamp pulses increased [Ca2+](i). The rate of decay of [Ca2+](i). was slowed by inhibition of the sarcoplasmic reticulum (SR) Ca2+-ATPase with cyclopiazonic acid (CPA). However, if the sarcolemmal Na+-Ca2+ exchanger and Ca2+-ATPase were inhibited then recovery of [Ca2+](i) was abolished showing that the SR Ca2+-ATPase alone cannot produce decay of [Ca2+](i). 3. In another series of experiments, Ca2+ release from the SR was induced with carbachol in a Ca2+-free solution. Under these conditions responses to repeated applications of carbachol could be obtained. In the presence of CPA, however, only the first application was effective. This suggests that the SR Ca2+-ATPase sequesters a significant amount of Ca2+ into the SR. 4. CPA slowed the rate of decay of [Ca2+](i) following carbachol addition by > 50%. Again, however, after a brief transient fall, decay was abolished when the Na+-Ca2+ exchanger and sarcolemmal Ca2+-ATPase were inhibited. 5. These data show that, although the SR Ca2+-ATPase contributes to the decay of [Ca2+](i), it cannot function effectively in the absence of Ca2+ removal from the cell. These data are discussed in the context of the superficial buffer barrier model in which Ca2+ is taken up into the SR and then released very close to sarcolemmal Ca2+ extrusion sites, i.e. the SR acting in series with the surface membrane extrusion mechanisms. We also suggest that the amount of filing of the SR influences the rate of Ca2+ removal.

关键词：钙/代谢钙/生理学钙信号/药物作用钙信号/生理学钙转运ATP酶类/生理学卡巴胆碱/药理学碳酰氰化物间-氯苯基腙/药理学动力学线粒体肌/药物作用线粒体肌/代谢线粒体肌/生理学肌平滑/细胞学肌平滑/生理学肌平滑/超微结构拟副交感神经药/药理学肌浆网/药物作用肌浆网/酶学肌浆网/生理学钠/生理学解偶联药/药理学子宫/细胞学子宫/生理学子宫/超微结构动物女(雌)性大鼠

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Effect of the microtubule polymerizing agent taxol on contraction, Ca²⁺ transient and L-type Ca²⁺ current in rat ventricular myocytes

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JOURNAL OF PHYSIOLOGY-LONDON 1999年第2期516卷 409-419页

作者： Howarth, FC Calaghan, SC Boyett, MR White, E Univ Leeds Sch Biomed Sci Leeds LS2 9JT W Yorkshire England

1. Microtubules form part of the cytoskeleton. Their role in adult ventricular myocytes is not well understood although microtubule proliferation has previously been linked with reduced contractile function. 2. We investigated the effect of the anti-tumour drug taxol, a known microtubule polymerizing agent, on Ca2+ handling in adult rat ventricular myocytes. 3. Treatment of cells with taxol caused proliferation of microtubules. 4. In taxol-treated cells there was a reduction in the amplitude of contraction, no significant effect on the amplitude of L-type Ca2+ current, but a significant reduction in the amplitude of the Ca2+ transient. 5. Caffeine was used to release Ca2+ from the sarcoplasmic reticulum (SR). There was a significant reduction in the ratio of electrically stimulated: caffeine-induced Ca2+ transients in taxol-treated cells. This observation is consistent with the hypothesis that taxol reduces fractional SR Ca2+ release. 6. We suggest that the negative inotropic effect of taxol may, at least in part, be the result of reduced release of Ca2+ from the SR. Microtubules may be important regulators of Ca2+ handling in the heart.

关键词：抗肿瘤药植物/药理学咖啡因/药理学钙通道/药物作用钙通道/代谢钙通道 L型钙信号/药物作用秋水仙碱/药理学抑制化学性电刺激心室/细胞学心室/药物作用心室/超微结构微管/药物作用微管/超微结构心肌收缩/药物作用心肌/细胞学心肌/代谢心肌/超微结构紫杉酚/药理学膜片钳术磷酸二酯酶抑制剂/药理学大鼠 Wistar 肌浆网/药物作用肌浆网/代谢动物男(雄)性大鼠

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