AIM:To investigate whether mitochondrial membrane potential (ΔΨm ) and the mitochondrial ap-optotic pathway are involved in the protective mechanism of Panax quinquefolium saponin ( PQS) against cardiomyocyte ap-optosis after ischemia/reperfusion ( I/R) injury in rat myocardium .METHODS: Ninety healthy male SD rats were ran-domly divided into sham group , I/R group, PQS (200 mg· kg -1 · d-1 ) +I/R group, cyclosporine A ( CsA) group, CsA (10 mg· kg-1 ) +I/R group and PQS +CsA +I/R group.The model of myocardial I/R injury in vivo was established by ligating the left anterior descending artery ( LAD) for 30 min followed by 120 min of reperfusion in the rats .The serum ac-tivity of lactate dehydrogenase ( LDH ) was measured by automatic chemistry analyzer .The myocardial infarct size was measured by Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining.Cardiomyocyte apoptosis was detected by in situ TDT-mediated dUTP nick end labeling (TUNEL).The protein levels of Bcl-2, Bax, cleaved caspase-3 and cytosol-ic cytochrome C were determined by Western blotting .ΔΨm was measured by laser scanning confocal microscopy and fluo-rescence microplate reader .RESULTS:Compared with I/R group, the serum content of LDH ,the infarction size in PQS+I/R group, CsA+I/R group and PQS +CsA+I/R group and the myocardial apoptotic index were decreased .Compared with I/R group, the fluorescence intensity of mitochondria after JC-1 staining was enhanced in PQS +I/R group, CsA+I/R group and PQS+CsA+I/R group, and the relative fluorescence units (RFU) ofΔΨm were improved in those 3 groups. In PQS+I/R group, CsA+I/R group and PQS+CsA+I/R group, the protein expression of Bcl-2 was increased, and that of Bax was decreased compared with I/R group.Moreover, in those 3 groups, the protein levels of cleaved-caspase-3 and cytosolic cytochrome C were decreased compared to I /R group, respectively.CONCLUSION:PQS attenuates myocardial injury and cardiomyocyte apoptosis during I /R, and the protective mechanisms of PQS were associated with the modulation ofΔΨm and the inhibition of mitochondrial apoptosis pathway .%目的：研究西洋参茎叶总皂苷（ PQS）对大鼠缺血/再灌注（ I/R）损伤后心肌细胞凋亡的影响，并从线粒体膜电位（ΔΨm ）及线粒体凋亡通路探讨其可能的机制。方法：健康雄性SD大鼠90只，随机分为假手术（sham）组、模型（I/R）组、PQS （200 mg· kg-1· d-1，灌胃6周）＋I/R组、环孢霉素A （CsA；10 mg· kg-1，再灌前10 min腹腔注射）组、CsA＋I/R组和PQS＋CsA＋I/R组，各组n＝15。除sham组和CsA组大鼠开胸后冠状动脉左前降支（ LAD）下穿线不结扎外，其余各组大鼠常规麻醉后，结扎LAD 30 min，再灌注120 min复制I/R模型。生化分析仪测血清乳酸脱氢酶（ LDH）含量，氯化三苯基四氮唑（ TTC）和伊文思蓝双染法测心梗面积，原位缺口末端标记法（ TUNEL）检测各组大鼠心肌细胞凋亡情况，Western blotting检测细胞凋亡相关蛋白的表达。采用JC-1作为荧光探针，用激光共聚焦显微镜和荧光酶标仪测定ΔΨm 水平。结果：与sham组比较，I/R组血清LDH活性、心梗面积和心肌细胞凋亡率均显著升高（P＜0．05）；与I/R组相比，PQS＋I/R组、CsA＋I/R组和PQS＋CsA＋I/R组血清LDH活性、心梗面积和心肌细胞凋亡率均显著降低（ P＜0．05）。 Western blotting结果显示，与sham组相比，I/R组心肌Bcl-2蛋白表达量降低，Bax、胞浆cytochrome C和cleaved caspase-3升高（均P＜0．05）；与I/R组相比，PQS＋I/R组、CsA＋I/R组和PQS＋CsA＋I/R组心肌Bcl-2蛋白表达量升高，Bax、胞浆cytochrome C及心肌cleaved caspase-3蛋白表达量均降低（P＜0．05）。激光共聚焦显微镜观察结果示，I/R组线粒体JC-1染色后红色荧光强度减弱，荧光酶标仪测相对荧光单位（RFU）较sham组降低（P＜0．05）；PQS＋I/R组、CsA＋I/R组和PQS＋CsA＋I/R组RFU均较I/R组升高（P＜0．05）。结论：PQS显著降低大鼠I/R后心肌细胞损伤，减少细胞凋亡，其机制与维持再灌注期ΔΨm 稳定、抑制线粒体凋亡通路的激活有关。
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