犬急性心肌缺血后左心室功能与抑凋亡蛋白Bcl-xl表达的研究

Changes of Expression of Bcl-xl and left ventricular function in experimental acute myocardial ischemia dogs

目的观察犬急性心肌缺血后左心室壁动度、射血功能、细胞凋亡与心肌组织中Bcl—xl表达的变化。方法犬30只随机分为实验组15只及对照组15只，实验组结扎左冠状动脉前降支近端，结扎时间分别为10，30，60min，每一时间点5只，对照组游离左冠状动脉前降支近端，不结扎。心肌组织行三苯四氮唑（TIE）染色，梗死区为黄白色，非梗死区为红色。超声心动图测定左室前壁增厚率及左心室射血分数，原位末端脱氧核苷酸转移酶介导的生物素脱氧尿嘧啶核苷酸缺口末端标记法（TUNEL）检测梗死区心肌组织凋亡细胞数，Western blotting检测梗死区心肌组织Bcl—xl的表达强度变化。结果TIE染色示左室前壁及部分前间隔染色为黄白色，其余区域为红色。实验组冠脉结扎后10rain，左室前壁增厚率降低，与对照组比较差异有统计学意义（P〈0．05）。左心室射血分数未发生明显改变，与对照组比较差异无统计学意义（P〉0．05）。冠脉结扎后30～60min，前壁增厚率降低与左心室射血分数进一步下降，与对照组比较差异有统计学意义（P〈0．01）。实验组在冠脉结扎后10min，梗死区心肌TUNEL阳性细胞数与对照组比较差异无统计学意义；冠脉结扎后30～60min，梗死区心肌TUNEL阳性细胞数明显增加，与对照组比较差异有显著统计学意义（P〈0．01）。实验组在冠脉结扎后30min，梗死区心肌Bcl—xl表达增高，与对照组比较差异有统计学意义（P〈0．05）。冠脉结扎后60min，梗死区心肌Bcl—xl表达明显增高，与对照组比较差异有显著统计学意义（P〈0．01）。结论急性心肌缺血后，心肌细胞凋亡可能为其早期病理改变，并且与心肌室壁动度与左室收缩功能降低有一定关系，同时抑凋亡基因Bcl—xl表达迅速增加，以对抗促凋亡基因的作用。

Objective To investigate changes of apaptosis and Caspase3 activity and the left ventricular ejection function and the regional myocardial dysfunction following acute ischemia in dogs. Methods Thirty dogs were divided into experiment and control groups. Dogs in experiment group were studied at 10, 30 and 60 min following left anterior descending coronary artery occlusion. Triphenyltetrazolium ehlorde（TTC）staining was used to identify ischemia myocardium. The left ventrieular ejection fraction and the degree of the increase in left ventrieula wall thickness were detected by cardiography. The percentage of apaptosis in regional left myocardial dysfunction was detected by terminal deoxynueleotidyl transferease - mediated biotinylated deoxyuridine triphosphate nick end labelling （TUNEL）. Western blotting was employed to detect Caspase3 activity. Results Anterior wall of left ventrieule and regional interventrieular septum in experiment group were ischemie. The degree of the increase in left ventrieula wall thickness in experiment group decreased at 10 min after coronary artery occlusion. （ P 〈 0.05） The left ventrieular ejection fration in experiment group had no change at 10min after coronary artery occlusion（ P 〉 0.05）.The left ventricular ejection fate and the degree of the increase in left ventrieula wall thickness decreased at 30min after coronary artery occlusion in experiment group. The positive cells of TUNEL detected in infarcted myocardial had no difference between experiment and control groups at 10 min（ P 〉 0.05）, and increased in experiment groups at 30 min after coronary artery occlusion（ P 〈 0.01）. The expression of Bcl - xl in infarcted myocardial in experiment group increased at 30rain and 60min after coronary artery occlusion （ P 〉 0.05 or P 〈 0.01 ）. Cell apoptosis may be the early pathologic changes following acute ischemia in dogs, which are related to the decrease in left ventricular ejection fraction and in left ventricula wall systolic thickness. At the same time, the expression of Bcl - xl increased, which may attributes to the inhibition of cardiomyocyte apoptosis.