ABSTRACT
Objective To evaluate the effect of activating adenosine A2A receptors on myocardial is-chemia-reperfusion ( I∕R) injury in diabetic rats and the relationship with autophagy. Methods Clean-grade healthy male Sprague-Dawley rats, aged 6 weeks, weighing 200-250 g, were studied. The diabetic rat model was established by intraperitoneal injection of 1％ streptozotocin 60 mg∕kg. Forty diabetic rats were divided into 4 groups ( n=10 each ) using a random number table method: sham operation group ( group Sham) , I∕R group ( group I∕R) , I∕R plus adenosine A2A receptor agonist CGS21680 group ( group CGS) , and I∕R plus CGS21680 plus adenosine A2A receptor antagonist ZM241385 group ( group CGS+ZM) . Myocardial I∕R was produced by occlusion of the left anterior descending branch of the coronary artery for 30 min followed by 120-min reperfusion. Adenosine A2A receptor agonist CGS2168010μg∕100g was in-travenously injected at 10 min before reperfusion in group CGS. CGS2168010 ug∕100g and ZM2413850. 2 mg∕kg were intravenously injected sequentially at 10 min before reperfusion in group CGS+ZM. Blood sam-ples were obtained at the end of reperfusion for determination of concentrations of creatine kinase-MB ( CK-MB), lactate dehydrogenase (LDH) and cardiac troponin I (cTnI) in serum (by enzyme-linked immu-nosorbent assay). The animals were sacrificed, and myocardial tissues were obtained for measurement of the percentage of myocardial infarct volume ( by TTC staining) and for determination of the expression of mi-crotubule-associated protein 1 light chain 3 Ⅰ ( LC3Ⅰ) , LC3 Ⅱ, p62 and Beclin-1 ( by Western blot) . LC3 Ⅱ∕LC3 Ⅰ ratio was calculated. Results Compared with group Sham, the serum CK-MB, LDH and cTnI concentrations and percentage of myocardial infarct volume were significantly increased, the expression of p62 and Beclin-1 was up-regulated, and the LC3Ⅱ∕LC3Ⅰratio was increased in group I∕R ( P<0. 05) . Compared with group I∕R, the concentrations of serum CK-MB, LDH and cTnI and percentage of myocardial infarct volume were significantly decreased, the expression of p62 and Beclin-1 was down-regulated, and the ratio of LC3Ⅱ∕LC3Ⅰwas increased in group CGS ( P<0. 05) , and no significant change was found in the pa-rameters mentioned above in group CGS+ZM (P>0. 05). Compared with group CGS, the concentrations of serum CK-MB, LDH and cTnI and percentage of myocardial infarct volume were significantly increased, the expression of p62 and Beclin-1 was down-regulated, and the ratio of LC3Ⅱ∕LC3Ⅰwas decreased in group CGS+ZM ( P<0. 05) . Conclusion Activating adenosine A2A receptors can mitigate myocardial I∕R injury, and the mechanism may be related to enhancing autophagy in diabetic rats.
ABSTRACT
Objective To investigate the effect of diabetes mellitus (DM) on adenosine postcondi-tioning-induced reduction of myocardial ischemia-reperfusion (I∕R) injury in rats. Methods Adult male Sprague-Dawley rats, weighing 230-260 g, were used in the study. Type 2 DM was induced by high-fat diet and intraperitoneal l％ streptozocin 35 mg∕kg and confirmed by fasting blood glucose concentration>16. 7 mmol∕L 72 h later. Eighteen rats with type 2 DM were divided into 3 groups (n= 6 each) using a ran-dom number table: sham operation group (DS group), I∕R group (DI∕R group) and adenosine postcondi-tioning group (DAP group). Eighteen healthy nondiabetic rats were selected and randomly divided into 3 groups (n= 6 each): sham operation group (NS group), I∕R group (NI∕R group) and adenosine postcon-ditioning group (NAP group). Myocardial I∕R was induced by 30 min occlusion of the left anterior descend-ing branch of coronary artery followed by 2 h of reperfusion. Venous blood samples were collected from the femoral vein at 2 h of reperfusion for measurement of plasma cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) concentrations (by enzyme-linked immunosorbent assay). The rats were then sacrificed im-mediately after blood sampling for determination of the myocardial ischemic area and infarct size. Results The plasma cTnI and CK-MB concentrations were significantly increased, and the percentage of myocardial infarct size was increased after myocardial I∕R in nondiabetic and diabetic rats. Adenosine postconditioning significantly decreased plasma cTnI and CK-MB concentrations and percentage of myocardial infarct size in nondiabetic and diabetic rats (P<0. 05). Compared with group NAP, the plasma concentrations of cTnI and CK-MB were significantly increased, and the percentage of myocardial infarct size was increased in group DAP (P<0. 05). Conclusion DM can weaken cardioprotection induced by adenosine postcondition-ing in rats.
ABSTRACT
Objective To evaluate the role of δ-opioid receptors in hydromorphone postcondition-ing-induced maintenance of electrophysiological stability during ischemia-reperfusion(I∕R)in isolated rat hearts. Methods Healthy male Sprague-Dawley rats, aged 2-3 months, weighing 280-360 g, were used in this study. The animals were anesthetized with intraperitoneal pentobarbital 60 mg∕kg. Their hearts were immediately removed and perfused in a Langendorff apparatus. Thirty-two isolated hearts were divided into 4 groups after successful preparation of Langendorff perfusion model(n=8 each)using a random number ta-ble: control group(group C), group I∕R, hydromorphone postconditioning group(group HP)and hydro-morphone plus δ-opioid receptor antagonist naltridole postconditioning group(group HNP). In HP and HNP groups, the hearts were perfused for 10 min with K-H solution containing 41 ng∕ml hydromorphone and 41 ng∕ml hydromorphone plus 5 μmol∕L naltridole, respectively, and then with K-H solution for 50 min. At 20 min of stabilization(T0)and 10, 25 and 60 min of reperfusion(T1-2), heart rate(HR), monophasic action potential(MAP)duration at 90% repolarization(MAPD90)of the two layers(endocar-dium, epicardium)of the anterior left ventricular wall were recorded. Transmural dispersion of repolariza-tion(TDR)was calculated. The development of arrhythmia, time for restoration of spontaneous heart beat and duration of arrhythmia were recorded during the period of reperfusion. Results Compared with group C, MAPD90of endocardium at T1-2and MAPD90of epicardium at T1were significantly prolonged in I∕R and HP groups, HR was significantly decreased at T2-3, MAPD90of endocardium and epicardium was prolonged at T1-3in group HNP, TDR was significantly enlarged at T1in group I∕R and at T2in group HNP, and TDR was decreased at T3in group HP(P<005). Compared with group I∕R, no significant change was found in arrhythmia score(P>005), the time for restoration of spontaneous heart beat was significantly shortened, and TDR was decreased at T1in HP and HNP groups, duration of arrhythmia was significantly shortened, and MAPD90of endocardium was shortened at T1in group HP, and HR was significantly decreased at T2-3, MAPD90of endocardium and epicardium was prolonged at T1-3, and TDR was decreased at T2-3in group HNP(P<005). Compared with group HP, no significant change was found in time for restoration of spon-taneous heart beat, duration of arrhythmia or arrhythmia score(P>005), HR was significantly decreased at T2-3, MAPD90of endocardium and epicardium was prolonged at T1-3, and TDR was increased at T3in group HNP(P<005). Conclusion The mechanism underlying hydromorphone postconditioning-induced maintenance of electrophysiological stability during I∕R is related to activating δ-opioid receptors in isolated rat hearts.