短期和长期运动预适应对力竭大鼠心肌损伤的保护作用

目的：研究短期和长期运动预适应对心肌细胞凋亡保护中发挥的作用及机制。方法：48只雄性SD大鼠随机分为对照组（C）、力竭组（E）、短期运动预适应组（S-EP）、长期运动预适应组（L-EP）。短期和长期运动预适应分别进行3 d和3周的反复间歇游泳训练方案。光镜下观察心肌细胞的结构改变；ELISA方法检测血清中缺血修饰白蛋白（IMA）、磷酸肌酸同工酶（CK-MB）含量；实时荧光定量PCR和Western blot方法检测心肌组织中TNF-α、Caspase-8、Caspase-3基因和蛋白表达；采用DNA原位末端标记（TUNEL）法观察心肌细胞的凋亡情况。结果：与C组相比，E组心肌细胞损伤严重，血清IMA、CK-MB含量及心肌组织中TNF-α、Caspase-8、Caspase-3 mRNA和蛋白表达升高（P<0.05）；与E组相比，S-EP组血清CK-MB及心肌TNF-α、Caspase-8mRNA明显降低（P<0.05），而蛋白表达无统计学差异，血清IMA及Caspase-3 mRNA和蛋白均下降不明显，无统计学意义（P>0.05），L-EP组血清IMA、CK-MB含量及心肌TNF-α、Caspase-8、Caspase-3 mRNA及蛋白明显降低，有统计学意义（P<0.05）；与S-EP组相比，L-EP组血清IMA、CK-MB含量及TNF-α、Caspase-8、Caspase-3 mRNA和蛋白明显下降，有统计学意义（P<0.05）。E组心肌细胞凋亡明显，S-EP组和L-EP组均能抑制凋亡，且L-EP组与S-EP组相比心肌凋亡明显减少。结论：短期和长期运动预适应均可减轻力竭后的心肌损伤，但短期运动预适应并未改变Caspase蛋白酶的表达，长期运动预适应明显抑制Caspase-8、3 mRNA表达，减少蛋白合成，从而发挥心肌保护效应，故长期运动预适应在抑制心肌细胞凋亡方面较短期运动预适应更强。

Protective effects of short-term and long-term exercise preconditioning on myocardial injury in rats

Objective: To study the role and mechanism of myocardial apoptosis after short-term and long-term exercise preconditioning.Methods: Forty-eight male SD rats were randomly divided into control group (C), exhaust group (E), short-exercise preconditioning (S-EP) and long-term exercise preconditioning group (L-EP). Short-term and long-term exercise preconditioning were conducted for 3 days and 3 weeks of repeated intermittent swimming training program. The changes of myocardial cells were observed under light microscope. The serum levels of ischemia-modified albumin(IMA) and creatine kinase-isoenzyme(CK-MB) were detected by ELISA. Real time fluorescence quantitative PCR and Western blot were used to detect the expressions of tumor necrosis factor-α(TNF-α),Caspase-8, Caspase-3 genes and proteins in myocardial tissue. The apoptosis of cardiomyocytes was observed by TUNEL method.Results: Compared with group C, group E had serious myocardial injury. The levels of serum IMA, CK-MB and the expressions of TNF-α, Caspase-8 and Caspase-3 in myocardium were increased (P<0.05). Compared with group E, serum CK-MB and TNF-α and Caspase-8 mRNA in S-EP group were significantly lower than those in group E (P<0.05), but there was no significant difference in serum IMA and Caspase-3 mRNA and protein (P>0.05). The levels of serum IMA, CK-MB and TNF-α, Caspase-8 and Caspase-3 mRNA in L-EP group were significantly lower than those in control group (P<0.05). The apoptosis of cardiomyocytes in group E was obvious. Short-term and long-term exercise preconditioning could inhibit apoptosis. Compared with S-EP group, the apoptosis of L-EP group was significantly decreased.Conclusion: Short-term and long-term exercise preconditioning can reduce myocardial injury after exhaustive exercise, but short-term exercise preconditioning does not alter the expression of Caspase protease. Long-term exercise preconditioning significantly inhibits Caspase-8, 3 mRNA expression and reduces protein synthesis. The inhibitive effects of long-term exercise preconditioning on myocardial cell apoptosis were stronger than those of short-term exercise preconditioning.