吗啡后处理对大鼠离体心脏缺血再灌注损伤的影响

Effects of morphine postconditioning on ischemia-reperfusion injury in isolated rat hearts

目的评价吗啡后处理对大鼠离体心脏缺血再灌注损伤的影响。方法雄性SD大鼠，体重180～200g，应用Langendorff灌流装置，采用全心停灌45min、再灌注60min的方法制备大鼠离体心脏缺血再灌注模型。实验一：取模型制备成功的心脏32个，随机分为4组（n=8）：Ⅰ组～Ⅳ组，Ⅰ组不予处理，Ⅱ组-Ⅳ组于再灌注即刻分别灌注含0．3、3．0和30μmol／L吗啡的K-H液10min，随后灌注正常K—H液50min；实验二：根据实验一的结果，选择对离体心脏缺血再灌注损伤影响最强的吗啡浓度，另取模型制备成功的心脏32个，随机分为4组（n=8）：Ⅰ组～Ⅳ组，Ⅰ组不予处理，Ⅱ组～Ⅳ组于再灌注即刻分别灌注含吗啡的K—H液5、10和20min，随后灌注正常K-H液50min；实验三：根据实验二的结果，选取对离体心脏缺血再灌注损伤影响最强的吗啡后处理方法。另取模型制备成功的心脏37个，随机分为5组：Ⅰ组（n=8）不予处理；Ⅱ组（n=8）、Ⅲ组-Ⅴ组（n=7）于再灌注即刻分别灌注含吗啡、10μmol／L非选择性阿片受体阻断剂纳洛酮和吗啡、5μmol／L选择性κ受体阻断剂nor-binahorphimine和吗啡、5μmol／L选择性8受体阻断剂naltrindole和吗啡的K-H液，各组均再灌注正常K-H液50min。于再灌注60min时测定心肌肌酸激酶同工酶（CK-MB）活性，计算心肌缺血危险区，梗塞区（IS／AAR）。结果根据实验一、二的结果于再灌注即刻灌注含3．0μmol／L吗啡的K-H液10min行后处理。实验三的结果：与Ⅰ组比较，Ⅱ组和Ⅴ组心肌IS／AAR和CK—MB活性降低，Ⅳ组心肌CK-MB活性降低（P〈0．05或0．01），Ⅲ组以上指标差异无统计学意义（P〉0．05）；与Ⅱ组比较，Ⅲ组和Ⅳ组心肌IS／AAR和CK-MB活性升高（P〈0．01），Ⅴ组上述指标差异无统计学意义（P〉0．05）。结论吗啡后处理可减轻大鼠离体心脏缺血再灌注损伤，此作用可能与激活心肌κ受体有关。

Objective To determine whether morphine postconditioning （MP） could protect the heart against ischemia reperfusion （I/R） injury and which specific type（s） of the opioid receptor is involved in the cardioprotective effect produced by MP. Methods Male SD rats weighing 180-200 g were killed after intraperitoneal heparin 500 U/kg. The hearts were immediately removed and passively perfused in a Langendorff apparatus with K-H solution gassed with 95% 02-5% CO2. HR and left ventricular systolic pressure （LVSP） were measured from a fluid-filled latex balloon in the left ventricle. Global myocardial ischemia was induced by interrupting perfusion for 45 min followed by 60 min reperfusion. The experiment was performed in 3 parts ： In Part Ⅰ 32 isolated rat hearts were randomly divided into 4 groups （n = 8 each）： group Ⅰcontrol received no treatment; group Ⅱ , Ⅲ , Ⅳ were first perfused with K-H solution containing morphine 0.3, 3.0 and 30 μmol/L respectively for 10 min immediately after the end of ischemia followed by 50 min normal K-H solution perfusion. In part Ⅱ , the concentration of morphine in K-H solution which provided the best cardio-protective effects was chosen according to the result of Part Ⅰ. , 32 isolated rat hearts were randomly divided into 4 groups （ n = 8 each） ： group Ⅰ received no treatment; group Ⅱ ,Ⅲ , Ⅳ were first perfused with K-H solution containing morphine for 5, 10, 20 min respectively immediately after ischemia followed by 50 min perfusion with normal K-H solution. In part Ⅲ, the MP method which provided the best cardio-proteetive effects was chosen according to the result of PartⅡ , 37 isolated rat hearts were randomly divided into 5 groups ： group Ⅰ control （ n = 8） ; group n - Ⅴ were first perfused for 10 min with K-H solution containing morphine （ Ⅱ, n = 8）/morphine ＋ naloxone 10 μmol/L（ Ⅲ , n = 7）/ morphine ＋ nor-binahorphimine 5μmol/L （specific κ receptor antagonist, n = 7 ）/morphine ＋ naltrindole 5 μmol/L （specific δ receptor antagonist, n = 7 ） followed by 50 min reperfusion with normal K-H solution. Myocardial CK-MB activity was measured and myocardial infarct size （IS/AAR） determined （by 2,3,5-triphenyl tetrazolium staining） at the end of 60 min reperfusion. Results The postconditioning with morphine 3.0 μmol/L perfusion for 10 min provided the best cardio-proteetive effects in terms of IS/AAR and myocardial release of CK-MB. Naloxone completely abolished the cardio-protective effects of MP. Nor-binahorphimine partly reversed the protective effect of MP, while naltrindole had no effects on MP. Conclusion MP protects the heart against I/R injury via activating κ receptor.