离体灌流大鼠心脏Na^＋／H^＋交换的意义

离体大鼠等容收缩心脏预灌流30min,再换用含20mmol/L NH_4Cl的K-H液灌流10min后,随机分为两组:(1)对照组(n=5): 恢复常规K-H液冲洗15min;(2)给药组(n=5):在常规K-H液冲洗时,加入0.5mmol/L amiloride以抑制Na~+/H~+交换。结果如下:预灌及NH_4Cl负荷阶段,两组血液动力学指标无明显差别;在冲洗时,对照组血液动力学指标逐渐恢复,而给药组心肌一直处于挛缩状态。对照组心肌组织Na~+、Ca~(2+)、K~+含量高于给药组;而心肌组织MDA及冠脉流出液中LDH活性则低于给药组。因此,酸负荷状态下,Na~+/H~+交换是pHi及生理活动恢复的重要调节机制,抑制这—过程,将加重心肌组织的损伤,以至于死亡。

Na+/H+ Exchange in the Isolated Perfused Rat Hearts and its Significance

After 30 min of stabilization, the Langendorff perfused isovolumic rat hearts were subjected to 20mmol/L NH4C1 loading for 10min followed by 15min of washout (n = 5) with or without 0.5mmol/L amiloride (n = 5). When external NH4+ was suddenly removed, the ventricular function was depressed accompanied with arrhythmia in both groups. Subsequently, the rapidly necovery of ventricular function correlated with accumulation of Na+ and Ca2+ in control group. However, amiloride (a Na+/H+ exchange inhibitor) inhibited the recovery of ventricular function significantly, and exacerbated myocardial damage indicated by much higher tissue MDA content and release of LDH. The phenomena may reflected the depression of the re-adjustment of the intracellulai acidification resulted from NH4G1 loading. It is concluded that Na+/H+ exchange system is present in isolated rat heart, and plays an important role in the regulation of intra-cellular pH and physiological activities.