Intermittent Exercise On Skeletal Muscle Apoptosis Related Genes Bax, Bcl-2 And Related Factors

The reasons and treatments to fatigue and injure during exercise is one of the major problems being studied in modern sports medicine.Skeletal muscles, as the motion power organs,can't avoid being suffered in exercise especially in high intensity peak volume exercise. Apoptosis as a micro reason in fatigue and injure during exercise, it is unclear whether it has different mechanisms between different fiber of skeletal muscle and what is the relationship among major mechanisms.In order to investigate the mechanism of apoptosis in skeletal muscle,the differences of reactive oxygen species(ROS), mitochondrial Ca²⁺ content, Bax,Bcl-2 gene expression and the relationship among them during one bout of interval exercise and interval training were studied in fast-twitch and slow-twitch skeletal muscles.Methods: 24 three months old Sprague-Dawley rats are randomly divided into three groups: Sedentary(n=8), one bout of interval exercise(n=8) and interval training(n=8).24 h after the last bout of exercise, the tibialis anterior and soleus muscles were removed for testing SOD activity,GSH-PX activity,MDA content,mitochondrial Ca²⁺ content and Bax,Bcl-2 gene expression in the tissue.Results:(1)Interval exercise and training resulted in the increase of Bax expression, but without significance. Bcl-2 expression decreased both in soleus and tibialis anterior muscles after interval exercise,but increased after interval training, both without statistical significance.Comparing two exercise groups, interval exercise resulted in Bcl-2 expression significantly decreased than in interval training group.Both interval exercise and interval training resulted in Bax/Bcl-2 ratio increased in both fast-twitch and slow-twitch skeletal muscle, but significance was only found in tibialis anterior muscle after interval exercise.(2)SOD activity increased both in tibialis anterior and soleus muscle after two kind of exercise,but SOD activity significantly increased only in tibialis anterior muscle after interval exercise(increased 48%,P<0.05).(3)MDA content very significantly increased in tibialis anterior muscle both after interval exercise and interval training, but no significance was found in soleus muscle.(4)There wasn't significant change after interval exercise and interval training to GSH-PX activity in skeletal muscle. Only found increasing trend in tibialis anterior muscle than in soleus, without significance.(5)After interval exercise only found mitochondrial Ca²⁺ content in tibialis anterior muscle very significantly increased than sedentary group by 100%(P, at the same time,significantly higher than in soleus(P<0.05). After interval training, there was not significant change to mitochondrial Ca²⁺ content in tibialis anterior and soleus muscle.Between two exercise group,only found mitochondrial Ca²⁺ content in tibialis anterior muscle very significantly increased after interval exercise than after interval training(P<0.01).(6)Pearson product-moment correlation analysis found, after interval exercise, in tibialis muscle SOD activity significantly minus correlated with Bax expression(P<0.05),mitochondrial Ca²⁺ content significantly plus correlated with Bax/Bcl-2 ratio(P<0.05); In soleus muscle,MDA content significantly plus correlated both with Bax and Bax/Bcl-2 ratio(P<0.05),GSH-PX activity significantly plus correlated with Bcl-2 expression(P<0.05).After interval training, in tibialis anterior muscle, only GSH-PX activity significantly minus correlated with both Bax and Bax/Bcl-2 ratio(P<0.05), and significantly plus correlated with Bcl-2(P<0.05);In soleus muscle, SOD activity significantly plus correlated with Bcl-2(P<0.05), but significantly minus correlated with Bax/Bcl-2 ratio(P<0.05), mitochondrial Ca²⁺ content both significantly minus correlated with Bax and Bax/Bcl-2 ratio(P<0.05).Conclusions:(1)High-intensity interval exercise lead to Bax expression increased more, but Bcl-2 expression decreased more in fast-twitch than in slow-twitch skeletal muscles,it's maybe the increasing of free radical accelerates the department of Bax and Bcl-2.,and reducing exercise ability in the end. After interval exercise, mitochondrial calcium overload more serious in fast-twitch skeletal muscle. Mitochondrial calcium overload may be another intracellular information conduction mechanism besides gene mechanism that cause fatigue in skeletal muscle during exercise.(2)After interval training,Bax expression decreased a little and Bcl-2 expression increased both in slow-twitch and fast-twitch skeletal muscles when compared with interval exercise, and it's more obviously in fast-twitch skeletal muscles, this may be the genic mechanism of interval training strengthens exercise ability by decreasing pro-apoptotic genes expression and increasing anti-apoptotic genes expression. At the same time,after interval training, the capacity of dealing with high intracellular Ca²⁺ content improved in skeletal muscles this may be anther intracellular information conduction mechanisms that interval training improved exercise ability.