Kümmel L
Acta Univ Carol Med (Praha). 1989;35(1-2):31-42.
Isolated rat heart cells permeabilized by digitonin were examined as an experimental model to study heart bioenergetics. The cells displayed good parameters of oxidative phosphorylation (acceptor control ratio ca. 8 with pyruvate + malate). High ATPase activity detected in the cells was characterized. The ATPase activity was Ca-dependent (optimum [free Ca] ca. 400 nM), and Mg was necessary for its full activity. Double reciprocal plot l/v vs. 1/[free Ca] at physiological [free Ca] was linear, thus showing free Ca to be a substrate for the ATPase (Km for Ca ca. 149 nM). Double reciprocal plot 1/v vs. 1/[ATP] was also liner, thus showing the ATPase activity could be ascribed to a single enzyme. The ATPase is supposed to represent Ca, Mg-ATPase of sarcoplasmic reticulum. The ATPase activity appeared to be functionally coupled to oxidative phosphorylation of the cells by apparently preferring ATP supplied by mitochondria (KmATP = 74 microM) to external ATP (KmATP = 169 microM; P less than 0.05). Apparent preference by oxidative phosphorylation for ADP supplied by the ATPase (KmATP = 45 microM) to external ADP (KmATP = 152 microM) was also manifested by significant difference (P less than 0.02) in Km.
用洋地黄皂苷使大鼠心脏细胞通透后，以此作为研究心脏生物能量学的实验模型进行了检测。这些细胞显示出良好的氧化磷酸化参数（丙酮酸 + 苹果酸存在时的受氢体控制率约为8）。对细胞中检测到的高ATP酶活性进行了表征。该ATP酶活性依赖于钙（最佳[游离钙]约为400 nM），镁对其充分活性是必需的。在生理[游离钙]条件下，双倒数作图l/v对1/[游离钙]呈线性，因此表明游离钙是该ATP酶的底物（钙的Km约为149 nM）。双倒数作图1/v对1/[ATP]也呈线性，因此表明该ATP酶活性可归因于单一酶。该ATP酶被认为代表肌浆网的钙、镁 - ATP酶。该ATP酶活性似乎通过明显优先选择线粒体提供的ATP（KmATP = 74 microM）而非外部ATP（KmATP = 169 microM；P < 0.05），在功能上与细胞的氧化磷酸化相偶联。氧化磷酸化对ATP酶提供的ADP（KmATP = 45 microM）而非外部ADP（KmATP = 152 microM）的明显偏好也通过Km的显著差异（P < 0.02）得以体现。
