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

To study the role and mechanism of myocardial apoptosis after short-term and long-term exercise preconditioning.

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.

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.

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.