2类多巴胺受体对心肌缺血后处理保护作用的影响及机制

目的：观察2类多巴胺受体（DR2）在心肌缺血后处理保护中的作用,并探讨其机制。方法：复制原代培养乳鼠心肌细胞缺血后处理模型,细胞随机分为正常组（Control）、缺血/再灌注组（I/R）、缺血后处理组（PC）、缺血后处理＋DR2激动剂组（PC＋Bro）、缺血后处理＋DR2抑制剂组（PC＋Hal）、缺血后处理＋DR2抑制剂＋激动剂组（PC＋Hal＋Bro）。比色法检测细胞培养液乳酸脱氢酶（LDH）、超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量;透射电镜观察细胞超微结构改变;流式细胞仪检测细胞凋亡变化;Western blot方法检测DR2蛋白表达、p-p38和p-JNK的活性。结果：与正常组相比,I/R能够增加DR2蛋白的表达,升高LDH活性和MDA含量,降低SOD活性,加重细胞损伤和细胞凋亡,上调p-p38和p-JNK的活性;与I/R组比较,PC进一步增加DR2蛋白的表达,降低LDH活性和MDA含量,增加SOD活性,减轻细胞损伤和细胞凋亡,下调p-p38和p-JNK的活性,Bro增强了PC的心肌保护作用,Hal则可取消Bro的这种作用。结论：DR2激活通过下调p-p38和p-JNK的活性参与缺血后处理对心肌缺血/再灌注损伤的保护作用。

The effects of DR2 on myocardial ischemic postconditioning and its underlying mechanisms

Objective： To study the effects of dopamin receptors-2 （DR2） on myocardial ischemic postcondifioning and explore its underlying mechanisms. Methods： The myocardial ischemic postconditioning （PC） model was established in cultured primary rat neonatal cardiomyocytes which were then randomly assigned in the following groups： Normal control group, Ischemia/repefusion （I/R） group, PC （ischemic postconditiordng） group, PC ＋Bro （Bmmocriptine,a DR2 antagonist） group, PC ＋ Hal （Haloperidol, a DR2 repressor ） and PC ＋ Hal＋ Bm groups. The lactate dehydrogenase （LDH） and supemxide dismutase （SOD） activity and malondialdehyde （MDA） content in cell medium were analyzed by colorimetry. The ceil ultrastructure changes were observed by transmission electron microscope. The ceil apoptesis was analyzed using flowcytometry. The protein expression level of DR2 and activity of p-p38 and p-JNK were detected by Western blot. Results： Compared with the normal control group, I/R increased the protein expression level of DR2, enhanced LDH activity and MDA content, promoted ceil in- jury and apoptosis, decreased SOD activity, up-regulated the activity of p-p38 and p-JNK. Compared with the I/R group, although PC further increased the expression of DR2 protein, it decreased LDH activity and MDA content, cell injury and apoptosis, increased SOD activity, down-regulated activity of p-p38 and p-JNK. Bromocriptine treatment further enhanced PC-induced cardioprotective effect, yet Hal addition at- tenuated this enhancing effect exerted by bromecriptine. Conclusion： The activation of DR2 is involved in the protective effect of ischemic postconditioning on myocardial ischemia/reperfusion injury through down-regtdating the activity of p-p38 and p-JNK.