Effects Of Different Intensity Of Exercises On Skeletal Muscle Apoptosis In Rats

Many studies have proven skeletal muscle cell undergo apoptosis under a broad range of physiological and pathphysiological conditions, such as development, disease and exercise. However, the mechanism of this phenomenon is not clear. In order to seek the mechanism of myoblast apotosis induced by exercise, this study investigated apoptosis occurred in different types of rat skeletal muscle after different intensity of exercises, as well as the role of free radical and mitochondria uptake calcium in myoblast apoptosis.Methods Forty male adult Sprague-Dawley rats are randomly divided into three groups: control(C,n=10), middle intensity exercise(ME, n=10) and high intensity exercise(HE, n=10). The rats of ME and HE group runon the treadmill to exhaust with the speed of 19. 3 m/min(76% Vo2max)and 26.8 m/min (92.3%Vo2max) respectively. The rats in control group and in exercise group are killed by decapitation respectively in quiet status and immediately after exercise, and 3ml of blood taken to be made into serum. The soleus and tibialis anterior muscles are removed to made into paraffin wax sample, electron microscopy sample, tissue homogenate and mitochondria homogenate. Then the SOD activity and MDA content in serum, tissue homogenate and the mitochondrial Ca2+ content are examined, Paraffin wax sections labeled by TUNEL, the apoptotic myonuclei detected by microscopy and the change of mynuclei ultrastructure examined under electron microscopy. Results(1) No TUNEL positive myonuclei is detected in muscle of the control group. In HE group, No rats are detected TUNEL positive myonuclei in tibialis anterior, but 6 rats among them are detected that in soleus. In ME group, only 2 rats are detected apoptosic myonuleus in tibialis anterior and in soleus respectively.(2) Apoptotic myonucleus displays an irregular shape and a highly condensed chromatin along the inner surface of the nuclear envelope in the electron microscopy examination.(3) ME group's SOD activity of soleus increased about 39% more than control group' s soleus (p<0.01), and is also apparently higher than that of tibialis anterior in the same group (p<0.01). The SOD activities in HE group are increase slightly but the difference is not significant. The SOD activity of serum is decreased after exercise, but there is no significant difference between different intensity exercise group.(4) MDA content of soleus and tibialis anterior are both increased significantly after two types of exercise intensity, but MDA content difference of soleus and tibialis anterior in the same group is not significant, neither does that difference between two exercise groups. MDA content of serum is decreased obviously after exercise, which is quite significant with the control group, while the deference between two exercise groups in not significant.(5) The mitochondrial Ca2+ in soleus is increased by 53% after middle intensity exercise(p<0.05), while there were only slight increase in the other groups, and the comparison of that with control group has no significance.Conclusion Slow-twitch muscle more prone to apoptosis after a acute middle intensity exhaustive exercise Acute middle intensity of exhaust exercise. The possible mechanism is the great accumulation of Ca2+ in mitochondrion trigger the apoptosic program, which results in the.