| Part one: The effects of ethyl pyruvate on cardiac function in ischemia/reperfusion injuryObjective To investigate the cardioprotective effects of ethyl pyruvate(EP) on ischemia/reperfusion(I/R) myocardium and its potential underlying mechanism in isolated rat heart. Methods Twenty-four male Sprague-Dawley(SD) rats weighing 200-250g were randomly divided into 3 groups(n=8,respectively):control group, I/R group, Ethyl pyruvate group.The animals were sacrificed and the hearts were immediately removed and mounted on Langendorff apparatus and perfused with Kerbs-Henseleit(K-H) solution saturated with 95%O2 and 5%CO2 at 37℃.Langendorff perfusion was used to induce the heart I/R injury. After 30 min stabilization, the injury was induced by 30 min global ischemia followed by 60min reperfusion. Ethyl pyruvate group was carried out with the same protocol as the I/R group except that it was supplied with 2mmol·L-1 ethyl pyruvate 15 min before ischemia and throughout reperfusion. Left ventricular systolic pressure(LVSP),±dp/dtmax,coronary flow(CF) were monitored before ischemia and at 10,30 and 60 min of reperfusion.At the end of 60 min reperfusion,coronary efluent was colected for determination of CK and LDH activity,and the hearts were removed for determination of myocardial ATP,MDA content and SOD activity. Results The baseline level of LVSP,±dp/dtmax,CF,were no difference among the three groups(P>0.05) .While in the period of reperfusion, the indexes of cardiac function including LVSP,±dp/dtmax and CF in ethyl pyruvate group were significantly better than I/R group(P<0.05). In the same time,ATP content and SOD activity were much better preserved in ethyl pyruvate group, and the level of CK , LDH and MDA content were lower in ethyl pyruvate group than I/R group(P<0.05). Conclusion Ethyl pyruvate offers better protection against I/R injury and can promote the recorvery of cardiac function in the isolated rat heart. Part two: The effects of ethyl pyruvate on apoptosis and expression of Bcl-2,Bax,NF-κB in ischemia/reperfusion injuryObjective To study the effects of ethyl pyruvate on cardiomyocyte apoptosis following ischemia reperfusion in vitro and on expression of Bcl-2,Bax,NF-κB proteins. Methods Isolated rat hearts were perfused in a Langendorff mode. Twenty-four rats were randomly divided into 3 groups(n=8,respectively): Normal group was perfused for 90min. In the ischemia/reperfusion (I/R) group, after 30 min stabilization the injury was induced by 30 min global ischemia followed by 30 min reperfusion. Ethyl pyruvate(EP) group was carried out with the same protocol as the I/R group except that it was supplied with 2 mmol·L-1 ethyl pyruvate 15 min before ischemia and throughout reperfusion. Myocardial apoptotic index(AI) was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method. Expression of anti-apoptotic protein Bcl-2 , pro-apoptotic protein Bax and NF-κB in cardiac myocytes was detected by immunohistochemistry method. Results compared with control group, the content of MDA, AI and the expression of Bcl-2,Bax proteins were increased in I/R group;while comparing with control group, the content of MDA, AI and the expression of bax protein were decreased obviously and the expression of Bcl-2 protein was upregulated in EP group(P<0.01). Conclusion These results demonstrate that ethyl pyruvate can inhibit cardiac myocytes apoptosis maybe via alleviating oxidative stress, upregulating Bcl-2 and downregulating Bax,NF-κB proteins. |
