| Objectives To investigate the preventive effects of Tetramethylpyrazine (TMP) on acute myocardial ischemia injury in rats, the extent of apoptosis in cardiomyocytes , and the expression of Bcl-2 /Bax protein, and to explore the possible mechanism of TMP on inhibiting apoptosis in cardiomyocytes.Methods All SD rats were divided into four groups, control group (sham operation group), occlusion group (model group), TMP group, Prop group. The acute myocardial ischemia injury were induced by ligation of the anterior descending branch of the left coronary artery (LCA). Eight rats were pretreated with TMP (20 mg/kg, iv), and 8 with Prop (Propranolol, Prop, 2 mg/kg, iv) 10 min before ligation. ECG lead II was recorded, and the levels of MB isoenzyme of creatine kinase (CK-MB) and lactate dehydrogenase (LDH) also were determined. The morphologic features of apoptotic myocardial cells were observed by transmission electron microscopy. Apoptotic myocytes were detected with the TUNEL method. The expression of Bcl-2 and Bax protein in myocardial cells was detected by immunohistochemistry. The changes of the parameters mentioned above at the different time points (2 h and 4 h after ligation) were observed in AMI rats. Results1. Coronary occlusion of rats led to obviously ischemia change of the ECG Compared with the occlusion group, TMP and Prop attenuated the ischemic changes of ECG and reduced the levels of serum CK-MB and LDH (P<0.05) .2. Two h after AMI, some ischemic changes were found morphologically, such as edema in myocardial cells, empty cavities in mitochondria, and partial lysis of broken myocardialfibrils. In TMP group, though some ischemic changes still existed, they were alleviated.3. No apoptotic positive cells were found in non-ischemic myocardial tissues, but the apoptotic positive cells in ischemic myocardium were detected 2 h and 4 h after AMI. The number of apoptotic positive cells (cells/section) increased with time elapsed. Compared with the control AMI rats, the number of TUNEL positive cells in AMI rats treated with TMP decreased significantly (29.12±3.67 in occlusion group versus 21.50±2.88 in TMP group in 2 h, and 41.71±3.73 in occlusion group versus 19.00±3.78 in TMP group in 4 h).4. The expression of Bcl-2 occured in these three groups except the control group. Compared with the occlusion group, the expression of Bcl-2 was increased in cardiomyocyte from TMP group after 2 h and 4 h respectively, with 6.88±0.35 (%) in occlusion group versus 11.89±0.74 (%) in TMP group in 2 h and 7.10±0.35 (%) in occlusion group versus 13.18±0.55 (%) in TMP group in 4 h, while the expression of Bax was not significantly changed in TMP group as compared to that in the occlusion group.Conclusions1. AMI induced the apoptosis in myocardial cells. The number of apoptosis cells increased with time elapsed.2. The administration of TMP and Prop 10 min before ligation decreased the number of apoptotic myocardial cells.3. TMP alleviated the acute myocardial ischemia injury in rats through decreasing the levels of LDH and CK-MB, protecting mitochondria of myocardial cells and stabilizing myocardial cellular membrane. The possible mechanism of this effect is via increasing the expression of Bcl-2 and raising the ratio of Bcl-2/Bax protein. In conclusion, TMP protected the ischemic myocardium effectively.
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