| Objective:To study the protection of ramipril,BQ-123 and their combination against myocardial ischemia/reperfusion(I/R) injury in vivo in anesthetized rats.Methods:Healthy male Wistar rats were divided into 5 groups randomly:①sham operated(sham) group;②I/R group;③ramipril(RAM) guoup;④BQ-123(BQ) group;⑤ramipril and BQ-123(R&B) group.All groups but not sham were subjected to 30 min ischemia/120 min reperfusion through ligation of the left anterior descending(LAD) coronary artery.Twenty four hours before ligation,ramipril(1 mg/kg) was given orally to rats in RAM and R&B groups.The same volume of normal saline was given to rats in other three groups.BQ-123(10μg/kg/min) was infused intravenously from 10 min before ligation to the end of 30 min ischemia to rats in BQ and R&B groups.The same volume of normal saline was given to other three groups. Rats in sham group was not subjects to I/R procedure.A leadⅡelectrocardiogram was monitored throughout the experiment and ventricular arrhythmia(VA) was recorded during ischemia.The activity of plasma creatine kinase(CK) and lactate dehydrogenase(LDH) was measured by spectrophotometer.Myocardial infarct size was measured by TTC staining. Changes of myocardial morphology were observed after HE staining. Apoptosis of cardiomyocyte was assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling(TUNEL) assay and confirmed by detection of DNA ladder formation.The expression of Bcl-2 and Bax was determined by immunohistochemistry.Activity of caspase 3 in myocardium was detected by spectrophotometer.Results:1.Effects of ramipril and BQ-123 on myocardial ischemia/reperfusion (I/R) injury in rats.In I/R group,the elevation of ST-segment was dramatically increased (p＜0.001);onset of ventricular premature contraction(VPC) and ventricular tachycardia(VT) were 5.10±0.71 and 6.05±1.65 min,durations of them were 19.94±3.56 and 13.72±5.06 min;incidences of VT and ventricular fibrillation (VF) were 100%respectively;activity of plasma CK and LDH was significantly enhanced;infarct size/area at risk(IS/AAR) and IS were 36.68±4.30%and 83.74±8.73 mg;apoptosis index(AI) of cardiomyocyte was 37.72±0.87%;the ratio of Bcl-2/Bax was 0.35±0.06;activity of caspase 3 in myocardium was 5265.70±387.56 U/μg.Compared with I/R group,the parameters in RAM and BQ groups were changed dramatically.The elevation of ST-segment was decreased(p＜0.01), onset of VPC(10.27±2.63;7.77±0.87) and VT(10.57±1.32;8.74±0.96 min) were delayed,durations of VPC(9.55±1.10;7.59±1.99 min) and VT (5.63±1.45;5.38±0.80 min) were shortened,incidences of VPC,VT and VF were decreased.Activity of plasma CK and LDH was decreased.IS (46.72±9.23;41.71±7.85 mg),IS/AAR(22.65±2.30;20.43±3.79%),AI (23.94±1.81;21.41±1.67%) and caspase 3(4070.04±417.86;3894.71±374.96 U/μg) were decreased respectively.The ratio of Bcl-2/Bax(0.75±0.13; 0.84±0.14) was increased.The morphology of myocardium was improved. DNA-laddering demonstrated that apoptosis of cardiomyocyte was attenuated.2.Effects of ramipril in combination with BQ-123 on myocardial I/R injuryCompared with I/R group,the R&B group was changed dramatically.The elevation of ST-segment was decreased(p＜0.001);onset of VPC(9.17±1.58 min) and VT(8.91±1.45 min) were delayed,durations of VPC(8.91±1.45 min) and VT(4.69±0.90 min) were shortened;incidences of VT(59%) and VF (12%) decreased;activity of plasma CK and LDH was significantly degraded; IS(31.09±6.08 mg),IS/AAR(15.83±4.67%),AI(15.68±1.45%) of cardiomyocyte and caspase 3(3501.62±266.79 U/μg) were decreased, respectively;the ratio of Bcl-2/Bax(0.92±0.13) was,increased.The morphology of myocardium was improved.DNA-laddering demonstrated that cardiomyocyte apoptosis was attenuated.Compared with RAM and BQ groups,the parameters of R&B group were changed dramatically.Mean arterial blood pressure(MAP) was increased in reperfusion 30 and 120min(p＜0.001);activity of plasma CK in ischemia 30 min and LDH in reperfusion 120 min were both decreased(p＜0.001);IS, IS/AAR,AI and caspase 3 were decreased respectively.The morphology of myocardial was improved.DNA-laddering demonstrated that cardiomyocyte apoptosis was attenuated.And compared with BQ group,onset of VPC was delayed(p＜0.05);compared with RAM group,duration of VPC was shorten (p＜0.01),the ratio of Bcl-2/Bax were risen(p＜0.05). Conclusions:1.The results documented that ramipril and BQ-123 protected myocardium from I/R injury by decreasing the elevation of ischemia-induced VA,decreasing the activities of CK,LDH and caspase 3,increasing the ratio of Bcl-2/Bax associated with reduced necrosis and apoptosis of cardiomyocytes.2.It was the first time to investigate the protective effects of ramipril in combination with BQ-123 on myocardial I/R injury in vivo.The results demonstrated that combined using these two agents may protect myocardium from I/R injury.The protective effects on decreasing the activities of CK, LDH and caspase 3,decreasing infrarct size and apoptosis were better than using ramipril and BQ-123 alone.
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