| Objective To observe effects of taurine and gradual reperfusion on the ischemia-reperfusion induced myocardial apoptosis and the relation to myocardial Caspase3activity in isolated rat hearts, and to explore whether the potential molecular mechanisms of the protective effects were through Akt, Erk pathway.Methods Isolated myocardial ischemia-reperfusion (I/R) model was replicated by Langendorff perfused rat heart. Sprague-Dawley rats were randomly divided into seven groups:Normal (Nor) group, I/R group, gradual reperfusion (GR) group, taurine of lower concentration (T20) group, taurine of higher concentration (T40) group, gradual reperfusion combined with taurine of lower concentration (GT20) group and gradual reperfusion combined with taurine of higher concentration (GT40) group. The cardiac function was recorded, including left ventricular developing pressure (LVDP),+dp/dtmax,-dp/dtmax and coronary flow (CF). The activity of LDH in coronary effluent and myocardial Caspase3were detected. Changes of myocardial morphology were observed after HE staining. The myocardial infarct size and cardiocyte apoptotic index (AI) were measured with TTC staining method and TUNEL. The expression levels of t-Akt, p-Akt, t-Erk and p-Erk were determined by western blot analysis at the end of reperfusion.Results:1. The myocardial ischemia-reperfusion induced apoptosis was reduced by taurine and gradual reperfusionCompared with Nor group, cardiac function of I/R group was inhibited significantly, LVDP,+dp/dtmax, dp/dtmax were decreased significantly during reperfusion except reperfusion30min (P<0.01), and CF was reduced. The myocardial infarct size was increased significantly (36.76±4.48vs0.04±0.09, P<0.01), the activity of LDH in coronary effluent (105.69±17.07vs3.98±0.62, P＜0.01), and myocardial Caspase3activity (2221±382vs528±137, P＜0.01) were increased remarkably, AI was increased significantly (49.64±4.68vs8.95±1.17, P＜0.01).Compared with I/R group, the parameters in GR, T20, T40, GT20and GT40groups were changed dramatically. The cardiac function were improved significantly, LVDP,+dp/dtmax,-dp/dtmax and CF were increased during reperfusion, the myocardial infarct size (17.32±2.24,20.62±5.23,8.57±2.33,11.11±2.85,4.21±1.94vs36.76±4.48, P＜0.01), the activity of LDH (58.02±13.31,90.13±17.09,62.51±9.53,18.39±6.74,16.30±2.94vs105.70±17.10), myocardial Caspase3activity (1280±285,1883±311,1481±282,1045±203,712±180vs2221±382, P＜0.05or P<0.01) and AI (34.03±3.46,37.26±3.29,30.49±8.32,23.60±6.00,11.78±2.78vs49.64±4.68, P<0.01) were reduced remarkably. The morphology of myocardium was improved.Compared with GR, T20and T40groups, myocardial infarct size, the activity of LDH and myocardial Caspase3, apoptosis of cardiomyocytes were further reduced.2. Akt pathway of isolated rat I/R heart was activated by gradual reperfusion and gradual reperfusion combined with taurineCompared with I/R group, the expression levels of p-Akt were upregulated in GR, GT20and GT40groups, and the expression level of p-Akt in GT40group was the highest. But there was no difference in the expression level of p-Erk in each group.Conclusion:1. I/R injury in isolated rat hearts was reduced by gradual reperfusion and taurine by promoting the recovery of cardiac function, reducing myocardial infarct size, decreasing the activity of LDH and myocardial Caspase3, reducing apoptosis of cardiomyocytes.2. The myocardial infarct size, the activity of LDH and myocardial Caspase3and apoptosis of cardiomyocytes were further reduced by GR combined with taurine. These protective effects were most obvious in GT40.3. The expression levels of p-Akt were upregulated, but there was no change in the expression levels of p-Erk in GR, GT20and GT40. The potential molecular mechanisms of the anti-apoptosis effect of GR and GR combined with taurine may be through the activation PI3K/Akt signal pathway, and then inhibition of Caspase3activity. |
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