Li Shu-Zhuang, Wu Feng, Wang Bo, Wei Geng-Ze, Jin Zhen-Xiao, Zang Yi-Min, Zhou Jing-Jun, Wong Tak-Ming
Department of Physiology, Fourth Military Medical University, Xi'an, 710032, China.
Eur J Pharmacol. 2007 Apr 30;561(1-3):14-22. doi: 10.1016/j.ejphar.2006.12.036. Epub 2007 Jan 20.
This study determined the role of the reverse mode Na(+)/Ca(2+) exchanger (NCX) in cardioprotection of metabolic inhibition preconditioning in isolated ventricular myocyctes. Activity of the reverse mode NCX was assessed by changes of Ca(2+) upon withdrawal of extracellular Na(+). Ca(2+) was measured by spectrofluorometry, using Fura-2 as Ca(2+) indicator. The amplitude of contraction and exclusion of trypan blue by myocytes served as indices of contractile function and viability, respectively. Firstly, NCX activity significantly decreased during simulated reperfusion after severe metabolic inhibition (index ischaemia) in myocytes subjected to metabolic inhibition preconditioning. This inhibitory effect on NCX activity correlated with the enhancing effect of metabolic inhibition preconditioning on cell viability following ischaemic insult. Treatment myocytes with E4031, an activator of reverse mode NCX, during index ischaemia and reperfusion attenuated the enhancing effects of metabolic inhibition preconditioning on cell contraction and viability. Secondly, NCX activity was significantly higher at the end of metabolic inhibition preconditioning. More importantly, E4031 pretreatment mimicked the beneficial effects of metabolic inhibition preconditioning in myocytes and ischaemic preconditioning in the isolated perfused heart, respectively, and these effects were abolished by KB-R7943, an inhibitor of reverse mode NCX. The results indicate that increased reverse mode NCX activity during preconditioning triggered cardioprotection, and reduced reverse mode NCX activity during reperfusion after index ischaemia conferred cardioprotection.
本研究确定了反向模式钠/钙交换体（NCX）在离体心室肌细胞代谢抑制预处理心脏保护中的作用。通过细胞外钠去除后细胞内钙（[Ca²⁺]i）的变化来评估反向模式NCX的活性。使用Fura-2作为钙指示剂，通过荧光分光光度法测量[Ca²⁺]i。心肌细胞的收缩幅度和台盼蓝排斥分别作为收缩功能和活力的指标。首先，在经历代谢抑制预处理的心肌细胞严重代谢抑制（指数性缺血）后的模拟再灌注期间，NCX活性显著降低。这种对NCX活性的抑制作用与代谢抑制预处理对缺血损伤后细胞活力的增强作用相关。在指数性缺血和再灌注期间，用反向模式NCX的激活剂E4031处理心肌细胞，减弱了代谢抑制预处理对细胞收缩和活力的增强作用。其次，在代谢抑制预处理结束时，NCX活性显著更高。更重要的是，E4031预处理分别模拟了心肌细胞中代谢抑制预处理和离体灌注心脏中缺血预处理的有益作用，并且这些作用被反向模式NCX的抑制剂KB-R7943消除。结果表明，预处理期间反向模式NCX活性增加触发了心脏保护作用，而指数性缺血后再灌注期间反向模式NCX活性降低赋予了心脏保护作用。
