The Agonist Of Delta Opoid Agonist-DADLE Confer Rabbit Myocardial Protection During Ischemia/Reperfusion Injury In Vitro

Background: There are many ways of myocardial protection during cardiac operation such as high chloride solution perfusion, high chloride solution of containing blood perfusion high chloride solution of containing warm blood perfusion used to induce the heart to arrest. Inhibiting inflammatory drugs were used in order to inhibit inflammatory factors. These methods have effects to some extent, but they are still to be improved. The secure time of cardiac operation is still limited several hours. The methods of myocardial protection used in clinic would cause ischemia/reperfusion injury to some extant except high chloride solution of containing warm blood perfusion persistently. The injuries would cause bad systolic, arrhythmia when they are big. Many learners are working hard to explore new effective methods to protect myocardium during cardiac operation. The delta receptor of opoid has the effect of ischemic preconditioning, decreasing metabolism, mimicking hibernation of mammal. The myocardium can bear ischemia for several months during hibernation while they can recover completely, when it become warm.The aim of the test was to justify if the agonist of delta opoid receptor-DADLE has the effect of decreasing degeneration, necrosis and apoptosis of myocardium during ischemia/reperfusion injury of adult rabbit's mode in vitro.Methods: Thirty healthy white adult rabbits of Japan were chosen and divided into three groups (each group having ten). The rabbits were anesthetized with pentobarbital (45mg/kg) and heparinized with heparin (700 u/kg).The heart was rapidly excised and immersed in ice-cold physiologicsalt solution (PSS)(prepared as reported ). Pulmonary artery was cannulated and linked with a bottle, thus the CF was recorded. The venae cavae and pulmonary vein were ligated. The aorta was cannulated in the Langendorff mode and the heart was perfused with PSS at 37℃. Perfusion pressure was maintained at 80mmHg. After Langendorrf mode was set up and worked 30 min, data of LVDP, CK, and LDH were recorded as guidelines. Next standard cardioplegia (group Ⅰ ), standard cardioplegia +DADLE (group Ⅱ) (agonist of 8 opoid receptor), standard cardioplegia + naloxone (Ⅲ) (injected into the rabbits before 30min of the hearts were excised) were used to induce the hearts to arrest accordingly. Perfusion pressure was maintained at 80mmHg.The quantity of perfusion was 60ml. The temperature of perfusion was at 4℃. After two hours of ischemia, three groups were reperfused with oxygenated physiologic salt solution (PSS). After the hearts were reperfused and worked 30min, data of LVDP, LDH, CK were recorded again and compared with those of before ischemia. After the test, some of heart tissue of left ventricle front wall was cut. The tissue was weighed with electron balance and reweighed after it was dried in a drier to value water content of the myocardium of the tissue. Water content = (1-dry weight/wet weight) 100%.Some of the tissue was used to inspect the apoptosis rate of it with flow cytometry. And still some tissue was to explore the changes of the tissue of ultrastructure with electron microscope.Results: Compared with cardioplegia alone, post-ischemic left ventricle developed pressure (LVDP), coronary flows (CF), cell apoptosis rate of myocardium, ultrastructure of myocardium were better in delta opoid agonist group(P<0.01), while the group of the antagonist was worse. There was no difference of LVDP among groups before ischemia (P>0.05). The result was 83.9±1.5mmHg,84.1±1.9mmHg,82.7±1.5mmHg(P>0.05).There was a significant difference among groups after ischemia (P<0.05). The result of after ischemia of LVDP was 37.9±1.7mmHgN 69.8 4.0mmHg, 23.4±3.1mmHg. The content of LDH was no significant before ischemia (P>0.05) while the result of after ischemia was significant (P<0.05). The result of LDH of pre-ischemia was 295.9±12.4u/L, 305.3 8.4u/L, 297.1±10.3 u/L (P>0.05). The content of LDH after ischemia was 1884.4±37.5 u/L, 1272.6±59.1u/L, 2764.4±27.7 u/L. The content of CK before ischemia was...