Wagenknecht B, Freudenrich C C, LeFurgey A, Lieberman M
Department of Cell Biology, Duke University Medical Center, Durham, NC 27710.
J Mol Cell Cardiol. 1994 Jul;26(7):797-808. doi: 10.1006/jmcc.1994.1097.
Calcium-free incubation followed by exposure to calcium damages naturally occurring cardiac muscle preparations irreversibly. Whether the observed calcium overload during calcium repletion is a primary cause for, or a secondary consequence of, sarcolemmal disruption and cell injury is controversial. We used cultured embryonic chicken heart muscle cells to correlate ionic, metabolic, and ultrastructural changes during calcium depletion (0Ca, 1 mM EGTA) and repletion. After 10 min of calcium depletion, intracellular Na increased four-fold above control levels, intracellular K decreased by 26%, total cell Ca decreased by 81%, and cytosolic ionized Ca concentration decreased by 87%. Within 10 min of subsequent calcium repletion, total cell Ca transiently increased to four-fold above control, cytosolic ionized Ca concentration transiently increased to twice control, and both Na and K returned toward control levels; by 3 h of calcium repletion, physiological cation (Na, K, Ca) contents were restored and adenine nucleotide contents were normal. Long-term (i.e. 120 min) calcium depletion did not significantly reduce cell ATP levels, but increased adenine nucleotide turnover as indicated by adenosine and lactate release; after 60 min of subsequent calcium repletion, ionic and metabolic parameters were returned to control levels. During calcium depletion (both short- and long-term) and subsequent repletion, no ultrastructural changes occurred. When Mg was also removed during calcium depletion, the ionic changes during depletion and subsequent repletion were enhanced. When 10 microM CCCP was present during calcium depletion and repletion, cytosolic ionized Ca concentration increased to six-fold above control with no increase in total cell Ca content, suggesting that the increased Ca is buffered, in part, by mitochondria. These results indicate that an increase in Ca per se, occurring when high energy phosphate levels and/or cellular Ca buffering capacity are maintained, does not seem to be associated with irreversible cell injury.
无钙孵育后再接触钙会不可逆地损伤天然存在的心肌标本。在钙再灌注过程中观察到的钙超载是肌膜破坏和细胞损伤的主要原因还是次要后果存在争议。我们使用培养的胚胎鸡心肌细胞来关联钙缺失（0Ca，1 mM EGTA）和再灌注过程中的离子、代谢及超微结构变化。钙缺失10分钟后，细胞内Na增加至对照水平的四倍以上，细胞内K减少26%，细胞总Ca减少81%，胞质游离Ca浓度减少87%。在随后的钙再灌注10分钟内，细胞总Ca短暂增加至对照水平的四倍，胞质游离Ca浓度短暂增加至对照水平的两倍，Na和K均恢复至对照水平；钙再灌注3小时后，生理性阳离子（Na、K、Ca）含量恢复，腺嘌呤核苷酸含量正常。长期（即120分钟）钙缺失并未显著降低细胞ATP水平，但如腺苷和乳酸释放所示，腺嘌呤核苷酸周转率增加；在随后的钙再灌注60分钟后，离子和代谢参数恢复至对照水平。在钙缺失（短期和长期）及随后的再灌注过程中，未发生超微结构变化。当在钙缺失期间也去除Mg时，缺失和随后再灌注期间的离子变化增强。当在钙缺失和再灌注期间存在10 microM CCCP时，胞质游离Ca浓度增加至对照水平的六倍，而细胞总Ca含量未增加，这表明增加的Ca部分由线粒体缓冲。这些结果表明，当高能磷酸水平和/或细胞Ca缓冲能力得以维持时，Ca本身的增加似乎与不可逆的细胞损伤无关。
