Effect Of RhBNP On Myocardial Ischemia And Reperfusion Myocyte Apoptosis In Rat Hearts

Objective:To explore the effects of brain natriuretic peptide retreatment on myocyte apoptosis in rat hearts with acute myocardial ischemia and reperfusion.Methods:24 Wistar rats were divided randomly into three groups(12 animals for each group):sham group,ischemia/reperfusion injury group and pretreatment with B-type natriuretic peptide group.The left anterior descending coronary artery(LAD)in all rats were ligated with slipknot by fine suture after thoracotomy, following treatments including 45 minutes'local myocardial ischemia and 180 minutes'reperfusion except SHAM group. In SHAM group, the slipknot around LAD kept into loop for 225 minutes. At the end of reperfusion, 4 rats were selected randomly from each group and 2ml blood was taken from rat abdominal aorta to test the level of cardiac troponin I. Myocardial infraction size(infraction size,IS%) was measured through double-staining with Evans blue and Triphenyltetrazolium chloride.Cardiac specimen was taken from the other 4 rats in each group, myocardial pathomorphology change was examined under lens microscope, the expressions of caspase-8 and caspase-3 in the myocardium of ischemia area were measured by Immunohistochemistry assay, apoptosis index of myocardium was detected by TUNEL.Results:1,cTnI: Compared to SHAM group, the level of cTnI in I/R group and rhBNP group increased markedly and significantly(P<0.01).Compared to I/R group, the level of cTnI in rhBNP group decreased significantly(7.94±1.09 VS 10.82±2.06,P=0.000<0.01).2 Myocardial infraction size: Compared to SHAM group, remarkable myocardial infarction was noted in I/R group and rhBNP group; Compared to I/R group, IS/AAR% decreased markedly in rhBNP group, the difference was statistically significant(23.20±3.78 VS 32.84±7.02,P<0.01). 3 Myocardial apoptosis index: Compared to SHAM group, myocardial apoptosis index in both I/R group and rhBNP group increased remarkably and significantly(P<0.01); Compared to rhBNP group, myocardial apoptosis index in I/R group increased remarkably and significantly(40.08±2.17 VS 21.94±5.57,P<0.01).4 Expressions of caspase-8 and caspase-3: Compared to SHAM group, expression of caspase-8(152.58±6.30 VS 174.75±3.36, P<0.01) and caspase-3(128.50±20.00 VS 174.75±3.36, P<0.01) increased remarkably in I/R group and rhBNP group; Compared to rhBNP group, there was a reduced expression of caspase-8 and caspase-3 protein caused by myocardial ischemia reperfusion in rhBNP group.Conclution:1,Pretreatment with rhBNP shortly before the onset of reperfusion not only reduces necrosis,but also attenuates myocardial apoptosis. RhBNP has been shown cardioprotective effects during rat myocardial ischemia/reperfusion.2,The pretreatment of B-type natriuretic peptide Can alleviate rat myocardium from injury by inhibiting the expression of caspase-8,easpase-3 and reducing myocardial apoptosis.