Li Q A, Altschuld R A, Stokes B T
Department of Physiological Chemistry, Ohio State University, Columbus 43210.
Am J Physiol. 1988 Aug;255(2 Pt 1):C162-8. doi: 10.1152/ajpcell.1988.255.2.C162.
Intracellular free calcium in adult rat heart ventricular myocytes was monitored by single cell fura-2 fluorescence microscopy. The average resting free calcium in rod-shaped quiescent cells was 125 nM (range 70-200 nM). When cells were deenergized with an inhibitor (amytal) and an uncoupler (carbonyl-cyanide m-chlorophenylhydrazone) of oxidative phosphorylation, there was a small but significant increase (125-380 nM) in intracellular free calcium during the transition to a highly contracted (square) rigor form. After the onset of contracture, which occurred 5-15 min after addition of the above compounds, the increase in free calcium was slow for the first 20 min, reaching a value of only 750 nM. Thereafter, the rate of increase accelerated and 50 min after contracture, free calcium was approximately 3 microM. The increase in free calcium was absolutely dependent on extracellular calcium but was not inhibited by high concentrations of verapamil (2-7 microM), suggesting influx via the Na+-Ca2+ exchange transporter as the cause of calcium increase. However, in calcium repletion protocols the rate of increase in sodium-loaded myocytes was greatly accelerated if cells were not depleted of ATP, confirming suggestions that ATP loss partially inhibits Na+-Ca2+ exchange.
通过单细胞fura-2荧光显微镜监测成年大鼠心室肌细胞内的游离钙。杆状静息细胞中的平均静息游离钙为125 nM（范围70 - 200 nM）。当用氧化磷酸化抑制剂（戊巴比妥）和解偶联剂（羰基氰化物间氯苯腙）使细胞失去能量时，在转变为高度收缩（方形）僵硬形式的过程中，细胞内游离钙有小幅但显著的增加（从125 nM增加到380 nM）。在添加上述化合物后5 - 15分钟出现挛缩开始后，游离钙的增加在前20分钟缓慢，仅达到750 nM的值。此后，增加速率加快，挛缩后50分钟，游离钙约为3 μM。游离钙的增加绝对依赖于细胞外钙，但不受高浓度维拉帕米（2 - 7 μM）的抑制，这表明通过钠钙交换转运体的内流是钙增加的原因。然而，在钙补充方案中，如果细胞未耗尽ATP，钠负荷心肌细胞中钙增加的速率会大大加快，这证实了ATP损失会部分抑制钠钙交换的观点。
