Ionic movement and tolerance to ischemia in congenital heart disease : Sodium movement via the Na^+/H^+ exchange during reoxygenation is a determinant of post-ischemic functional recovery in the rat myocardium

目的：为了确定复氧过程中钠离子运动是否是缺血后心功能恢复的决定因素，我们检测了i）再灌注或复氧过程中Na^+/H^+交换抑制对缺血后心功能恢复的影响，以及ii）Na+/HCO_3^-协同转运蛋白参与钠离子运动。用碳酸氢盐缓冲液对离体大鼠心脏进行Langendorff灌流，并在常温（37 ℃）下进行20分钟的全脑缺血，然后在常温（37℃）下进行再灌注。i）在再灌注的前10分钟（方案I）或缺氧再灌注5分钟后10分钟（方案II）给予100 μM二甲基阿米洛利（DMA）。ii）在再灌注的前10分钟期间使用不含碳酸氢盐的HEPES缓冲液（方案III）。所有的方案随后均进行25分钟的常氧再灌注。i）在方案I和II中，DMA组的左心室发展压（%LVDP）的缺血后恢复显著大于对照组。（方案中分别为68.6± 5.9%和52.0± 6.1%，方案II中分别为66.6± 2.8%和52.0± 5.5%）。在方案III中，无碳酸氢盐组和对照组之间没有差异（分别为35.9±4.9和24.7± 6.7%）。结论：在复氧过程中，通过Na^+/H^+交换的钠离子运动是缺血后心功能恢复的决定因素。Na^+/HCO_3^-协同转运蛋白可能不参与再灌注过程中的钠离子运动。

Objectives : To determine whether or not sodium ion movement during reoxygenation is a determinant of post-ischemic recovery of cardiac function, we examined i) the effect of Na^+/H^+ exchange inhibition during reperfusion or reoxygenation on post-ischemic recovery of cardiac function and ii) the involvement of Na+/HCO_3^-cotransporter in the sodium ion movement.Methods : Isolated rat hearts were Langendorff-perfused with Krebs-Henseleit bicarbonate buffer and subjected to 20 minutes of normothermic (37C) global ischemia followed by normothermic (37℃) reperfusion. i) 100 μM dimethyl amiloride (DMA) was given during the first 10 min of reperfusion (protocol I) or for 10 minutes after 5-minute hypoxic reperfusion (protocol II). ii) a bicarbonate-free HEPES buffer was used during the first 10 minutes of reperfusion (protocol III). All the protocols were then followed by 25 minutes of noromoxic reperfusion.Results : i) In protocols I and II, the post-ischemic recovery of left ventricular developed pressure (%LVDP) was significantly greater in the DMA group than in the control group (68.6±5.9 vs. 52.0±6.1%, respectively in protocol Land 66.6±2.8 vs. 52.0±5.5%, respectively in protocol II). In protocol III, there was no difference between the bicarbonate-free group and the control group (35.9±4.9 vs. 24.7±6.7%, respectively).Conclusions : Sodium ion movement via the Na^+/H^+ exchange during reoxygenation is a determinant of post-ischemic recovery of cardiac function. The Na^+/HCO_3^- cotransporter may not be involved in the sodium ion movement during reperfusion.