Roles of intracellular Ca^<2+> in genesis of life-threatening arrhythmia.

豚鼠和Pst分离的心肌细胞胞浆钙阶梯酶用钙敏感的荧光染料FURA2研究了单个心肌细胞内钙离子浓度的动态变化，以阐明哺乳动物心脏张力阶梯现象的机制。静息3min后，1.0Hz的刺激使豚鼠心肌细胞出现(Ca^&lt；2+)i瞬变的上行阶梯，而大鼠心肌细胞出现[Ca^&lt；2+]i的下降阶梯。在相同的刺激方案下，肌浆网(SR)抑制剂ryanodine(1 Um)可显著抑制大鼠心肌细胞[Ca~(2+)]i的水平，但对豚鼠心肌细胞[Ca~(2+)]i的瞬变无明显影响。这些结果表明，在大鼠心肌细胞中，SR在负性收缩阶梯现象的发生中起重要作用，而在豚鼠心肌细胞中，Ca~(2+)通过盐膜的运动是…。在单个豚鼠心肌细胞氧化磷酸化恢复后细胞内钙离子浓度([Ca^&lt；2+&gt；]i)的变化。为了阐明再灌注性心律失常的机制，我们用钙敏感的荧光染料FURA2研究了单个豚鼠心肌细胞氧化磷酸化恢复后[Ca^&lt；2+]i瞬变的动态变化。DNP(0.1 mM)作用5分钟后，细胞氧化磷酸化恢复，收缩和舒张期[Ca^&lt；2+&gt；]i显著升高，并伴随着自发性收缩波和膜电位的波动。在洗脱液中加入1uM的ryanodine，几乎完全消除了[Ca^&lt；2+]i和膜电位波动的发生。这些结果表明，肌浆网钙离子的释放参与了氧化磷酸化恢复后[Ca^&lt；2+&gt；]i和膜电位的波动。较少

Cytosolic Calcium Stairacase in Ventricular Myocytes Isolated from Guinea-pigs and Psts. Dynamic changes in cytosolic calcium concenyration ([Ca^<2+>]) in single myocytes were investigated using a ca^<2+> sensitive fluorescence dye, fura2, to elucidate the mechanism of the tension staircase phenomenon of mammalian hearts. A stimulation train at 1.0 H_z after a 3 min rest period produced an ascending staircase of (Ca^<2+>]i transients in guinea-pig myocytes, while a descending staircase of [Ca^<2+>]i transients in rat myocytes. During the same stimulation protocol, an inhibitor of the sarcoplasmic reticulum (the SR), ryanodine (1 uM), sigh, ficantly depressed the leve of [Ca^<2+>]i in rat myocytes, while did not appreciably affected [Ca^<2+>]i transients in guinea-pig myocytes. These results suggested that in rat myocytes the SR plays important role in the genesis of the negative contractile staircase phenomenon, while in guinea-pig myocytes the Ca^<2+> movement across the salcolemma is … More important for the genesis of the positive contractile staircase phenomenon.Flutuation of Cytosolic Calcium Concentration ([Ca^<2+>]i) Following Resumption of Oxidative phosphorylation in Single Guinea-pig Myocytes.Dynamics of [Ca^<2+>]i transients following resumption of oxidative phosphorylation were examined in single guinea-pig myocytes using a Ca^<2+>-sensitive fluorescent dye, fura2, in order to elucidate mechanisms of the reperfusion arrhythmia. Resumption of oxidative phosphorylation, produced by a wash-out after 5-min exposure to DNP(0.1 mM), caused a significant rise of both systolic and diastolic [Ca^<2+>]i associated with spatially and gemetrically inhomogenous fluctuations of [Ca^<2+>]i, which were accompanied by the spontaneous contractile wave and fluctuation of the membrane potential. An addition of ryanodine(1uM) to the wash-out solution, almost completely abolished the occurrence of both the [Ca^<2+>]i and membrane potential fluctuations. These results suggest that the Ca^<2+> release from the sarcoplasmic reticulum is involved in the fluctuation of [Ca^<2+>]i and membrane potential that occurs following resumption of oxdative phosphorylation. Less