多巴胺受体2减轻离体大鼠心肌缺血/再灌注损伤

DR2 attenuates myocardial ischemia / reperfusion injury of rats in vitro

目的观察多巴胺受体2(DR2)对离体大鼠心肌缺血/再灌注(I/R)损伤的影响及其可能机制。方法将大鼠40只,每组n=10,随机分成对照组(control)、I/R组、10μmol/L Bromocriptine(DR2激动剂)组(Bro),10μmol/L Haloperidol(DR2抑制剂)组(Hal)。用Langendorff离体灌流装置,复制大鼠心肌I/R损伤模型。Powerlab生理记录仪记录心功能;比色法测定冠脉流出液LDH、CK活性和心肌组织匀浆SOD活性以及MDA含量;TUNEL染色检测心肌细胞凋亡;Western blot检测DR2、Bcl-2、caspase-3和caspase-9蛋白的表达。结果与对照组比较,I/R组DR2、Bcl-2、caspase-3和caspase-9蛋白表达、LDH和CK活性、MDA含量和细胞凋亡率均增加(P<0.01),唯有SOD活性降低,心功能减弱(P<0.01)。与I/R组比较,Bro降低LDH和CK活性、MDA含量、细胞凋亡率、caspase-3和caspase-9的表达,升高SOD活性,改善心功能和进一步增加Bcl-2的表达(P<0.01);Hal对上述指标影响不显著。结论 DR2可减轻心肌I/R损伤,其机制与抗氧化、清除自由基、上调Bcl-2表达以及下调caspase-3和caspase-9的表达有关。

Objective To observe the effects of dopamine receptors-2 （DR2） on the myocardial ischemia/reperfusion （I/R） injury in rats and to study the possible mechanisms.Methods 40 Wistar rats were randomly divided into 4 groups （n =10）：control group,I/R group,Bromocriptine group （Bro） and Haloperidol group （Hal）.Myocardial ischemia/reperfusion injury of isolated rats was induced by Langendorff system; The heart function was recored by Powerlab ; LDH,CK activities of coronary effluent and SOD activity and MDA content of myocardial tissue homogenate were measured by colorimetric method; Myocardial cell apoptosis was detected by TUNEL staining; The expression of DR2,Bcl-2,caspase-3 and caspase-9 was detected by Western blot.Results Compared with control group,the expressions of DR2,Bcl-2,caspase-3,caspase-9,the activity of LDH and CK,the MDA content,the rate of cell apoptosis were increased （P ＜0.01）,but the SOD activity and heart function were decreased in the I/R group （P ＜ 0.01）.Compared with I/R group,Bro decreased the activity of LDH and CK,the MDA content,the rate of cell apoptosis,the expression of caspase-3 and caspase-9,increased the SOD activity and Bcl-2 expressions,improved heart function （P ＜ 0.01）.Hal did not change the above indexes.Conclusions DR2 inhibites I/R injury through antioxidation that is poteintially explained by scavenging free radical,up-regulation of Bcl-2 expressions and down-regulation of caspase-3 and caspase-9 expression.