Objective To investigate whether the agonist of delta opoid receptor D-Ala(2),D-Leu(5) enkephalin (DADLE) has the effect of decreasing myocardial injury during ischemia-reperfusion of adult rabbits’ myocardium，so that a new mehanism and way to myocardial protection could be found. Methods Langendorff model was used during the experiment. Thirty rabbits were divided into three groups randomly (each group 10 rabbits). Control group: St.Thomas Ⅱ cardioplegic solution was used; group 1: St.Thomas Ⅱ cardioplegic solution and DADLE (1mg/kg) were used; group 2: St.Thomas Ⅱ cardioplegic solution and naloxone(3mg/kg) were used to induce the hearts to arrest respectively. After arrest the hearts were reperfused respectively. Data of left ventricle development pressure(LVDP) was recorded before and after ischemia. Biochemical indicators of myocardium, lactate dehydrogenase(LDH) were detected before and after ischemia. Some myocardial tissues were used to explore the changes of the tissue of ultrastructure with electron microscope，when the experiment was over. Still some myocardial tissues were to be detected by flow cytometer to evaluate the apoptosis of the myocardium. Results The LDH and LVDP showed significant difference among three groups after ischemia(Plt;0.05); LVDP in group 1 was higher than those in group 2 and control group(69.8±5.8 mmHg vs. 23.4±3.9 mmHg; 69.8±5.8 mmHg vs. 37.9±4.7 mmHg; Plt;0.05), the LDH in group 1 was lower than those in group 2 and control group(1 272.6±59.1 U/L vs. 2 764.4±27.7 U/L, 1 272.6±59.1 U/L vs. 1 884.4±37.5 U/L; Plt;0.05). The apoptosis rate in group 1 was lower than those in group 2 and control group. As could be shown from the ultrastructure: mitochondria structure was nearly normal in group 1; mitochondria structure was injuried severely in group 2; there was a minor injury in control group. Conclusion Agonist of δ opoid receptor DADLE in cardioplegic solution could induce hibernation, which has myocardial protection effect during ischemia-reperfusion injury.
Myocardial stunning is the main pathological basis of heart dysfunction after open heart operation, its exact pathogenesis hasn’t been clarified until today.In recent years,the molecular and cellular studies have revealed possibly crucial pathogenesis of myocardial stunning that delayed recovery of myocardial glucose oxidation causes intracellular H + accumulation which augments H + Na + exchange thus leading to [Na +] i overload.[Na +] i overload increases Na + Ca 2+ exchange resulting in t...