缺血后功能低下大鼠心肌钙与水含量的变化及高渗甘露醇的影响

缺血后心室功能减低(myocardial stunning)的发生机制迄今尚不明了。本实验以 Lang-cndorff 法在离体灌流的大鼠心脏,研究了全心缺血20min 及再灌注40min 后心肌 Ca~(2+)、Na~+K~+、Mg~(2+)及 H_2O 含量的变化,以及高渗甘露醇对缺血后功能低下心肌的影响。实验发现:(1)缺血/再灌注后心肌组织中 Ca~(2+),H_2O 的含量与非缺血组相比分别增加42%(P<0.01)及7.6%(P0.05)。(2)于再灌注同时给予12%高渗甘露醇可明显改善缺血后心室功能:再灌注40min 时,心率-左室压乘积恢复达缺血前的85%,而不给甘露醇仅恢复66.3%(p<0.01);高渗甘露醇同时消除了缺血后功能低下心肌中 Ca~(2+)超负荷与心肌水肿,此现象提示缺血/再灌注引起的肌膜非特异性通透性改变,很可能是钙进入细胞内的路径之一。本研究结果表明,心肌 Ca~(2+)超负荷及轻度心肌水肿参与了缺血后心室功能低下,高渗甘露醇在离体大鼠心脏可明显改善缺血后功能低下心肌的功能,此作用至少部分是由于其具有减低心肌钙与水含量的效应。

CHANGES IN CALCIUM AND WEATER CENTENT OF STUNNED MYOCARDIUM AND EFFECTS OF HYPEROSMOTIC MANNITOL IN RAT HEART

In this study we investigated changes in myocardial electrolytes and watercontents following 20 min of global ischemia and 40 min reperfusion in isolatedrat hearts perfused by Langendorff procedure.After ischemia and reperfusion,calcium and water contents in myocardium increased by 42%(P<0.01)and 7.6%(P<0.05)respectively as compared with nonischemic myocardium,but sodium,potassium and magnesium in myocardial tissue did not change significantly(P>0.05).When hyperosmotic mannitol(12%)was infused at the beginning of reper-fusion and persisted for 25 min,postischemic left ventricular function was improvedsignificantly.At 40 min of reperfusion,heart rate-left ventricular pressure pro-duct,an index of ventricular function,recovered to 85% of preischemia,and only66.3% recovery was seen in postischemic heart without mannitol(P<0.01).Inaddition,hyperosmotic mannitol caused marked decreases in myocardial calcium,water and other cations,suggesting that nonspecific sarcolemmal permeabilitychanges induced by ischemia/reperfusion probably is one of entry routes of calciuminto the cell.We conclude that calcium overload with mild myocardial edema is in-volved in myocardial stunning and hyperosmotic mannitol can improve the functionof stunned myocardium in isolated rat heart,which is,at least partially,due tothe reduction of myocardial calcium overload and swelling.