IMPROVEMENT OF ISCHEMIC TOLERANCE AND COLD PRESERVATION OF AGED MYOCARDIUM BY TRANSFECTION OF HEAT-SHOCK PROTEIN GENE

1.缺血耐受性随年龄增长而降低：分析了12、50和100周龄Fischer 344大鼠心脏左心功能和能量代谢产物的恢复、心肌酶(CPK和LDH)的释放以及缺血再灌注性心律失常。心肌缺血15~25min，再灌流30min。功能和代谢产物的恢复以及酶的释放显示出随年龄增长的缺血耐受性下降。在老年大鼠心脏中，缺血再灌注性心律失常的恶性程度也更高。结论：1.在长时间缺血前进行的缺血或低氧预适应对老年心脏没有任何有益的影响，甚至加重心肌损伤。基因转染法：热休克蛋白(HSP)基因转染组只有30%的细胞检测到HSP。这一百分比在24、48或72小时后无差异。当阳离子HvJ-脂质体为…时使用越多，效率提高越不明显。抗HSP抗体免疫细胞化学分析显示，HSP在内皮细胞中的阳性率较高，提示阳离子HVJ-脂质体可能在到达肌细胞之前就已被捕获到内皮细胞中。转HSP基因心脏冷停搏液和缺血再灌注损伤后的保存：尽管转HSP基因不能减少缺血再灌注性心律失常的发生，但转HSP基因对冷停搏液10min再保存2小时的心脏功能和代谢产物的恢复及酶的释放有促进作用。而缺血25min和再灌流30min心脏功能和代谢产物的恢复、酶的释放以及缺血再灌注性心律失常的恢复仅有不同程度的改善。心肌细胞模拟缺血：在任何年龄段的心肌细胞中，转导HSP基因的心肌细胞在模拟缺血3min(低氧，pH 6.5，乳酸20 mM，k12 mM)后，细胞内钙的增加减弱，细胞运动的恢复加快。较少

1. Decrease in ischemic tolerance with aging: Recovery of left ventricular function and energy metabolites, release of myocardial enzymes (CPK and LDH), and ischemia-reperfusion arrhythmias were analyzed in hearts isolated from 12, 50 or 100 week-old Fischer 344 rats. Hearts were subjected to 15 to 25 min of ischemia and 30 min of reperfusion according to the langendorff technique. Recovery of function and metabolites and release of enzymes demonstrated age-dependent decrease in ischemic tolerance. Ischemic-reperfusion arrhythmias were also more malignant in older rat hearts. Ischemic or hypoxic preconditioning performed before prolonged ischemia did not have any beneficial effects or even deteriorated myocardial damage in older hearts.2. Gene transfection: Heat shock protein (HSP) was detected only 30% of myocytes transfected with HSP gene using HVJ-liposome+plasmid methods. This percentage was not different between 24, 48 or 72 hours after transfection. When cationic HVJ-liposome was … More used, efficiency was not improved remarkably. Immunocytochemical analysis with anti-HSP antibody revealed that HSP was detected with high incidence in endothelial cells, which suggested cationic HVJ-liposome might be trapped in the endothelial cells before reaching to myocytes.3. Preservation after cold cardioplegia and iscchemia-reperfusion injury in HSP-transfected heats: Recovery of function and metabolites and release of enzymes in hearts subjected to 10 min cold cardioplegia followed by 2 hours preservation were tended to be improved when hearts of any age were transfected with HSP gene, although ischemia-reperfusion arrhythmias were not decreased by HSP transfection. On the other hand, recovery of function and metabolites, release of enzymes, and ischemia-reperfusion arrhythmias in hearts subjected to 25 min of ischemia and 30 min of reperfusion showed only insignificant improvement.4. Simulated ischemia in isolated myocytes: In myocytes of any age that were transfected with HSP gene, increase in intracellular Ca was attenuated and recovery of cell motion was improved after 3 min of simulated ischemia (hypoxia, pH6.5, lactate 20mM, k12mM). Less