Hypoxia,Exercise Effect On Apoptosis And The Expression Of Bcl-2 And Bax In Skeletal Muscle Of SD Rats

The purpose of this study was to investigate skeletal muscle apoptosis under hypoxia and different exercises by HE stain, by the terminal deoxynucleotidyl transferase assay, by electrophoretic detection of fragmented DNA and by immunohistochemistry. At the same time, the study researched hypoxia and eccentric exercise-induced damage in skeletal muscle of the rats from the angle of apoptosis.128 female Sprague-Dawley rats (7-week old) were divided into two groups as the objects of this study: unexhausted training groups and exhausting eccentric exercise groups. Furthermore, unexhausted training group were randomly divided into 7 groups (n=8): (1)unexhausted control(UC); (2)hypoxic unexhausted control(HUC), were divided into 4-day and 7-day two groups; (3)normal oxygen training group(OT), were divided into 4-day and 7-day two groups; (4)hypoxic unexhausted training group(HT), included 4-day and 7-day two groups. The groups of OT and HT were trained for 1h/day on the treadmill (20meter/min, +10。Uphill running). As the unexhauted training groups, all rats under hypoxia were laid in hypoxic chamber. They were accommodated to this condition for 3 days first, and then they were divided into the hypoxic sedentary control groups (killed on 0, 1, 2, 4, 7 days after exercise, HC) and hypoxic exhausting exercise groups (killed immediately and on 1, 2, 4, 7 days after a bout of exhausting exercise, He). As for the normoxic groups, they included one sedentary control group(EC) and five exhausting exercise groups (killed immediately and on 1, 2, 4, 7 days after a bout of exhausting exercise, OE). All the rats in the exercise groups performed exhausting exercises under normoxic condition. All the rats in hypoxic groups were placed in the hypoxic chamber in PO2 12.7% (corresponding to the altitude of 4000m), and all rats fed food and water ad libitum.The main results of unexhausted training groups are as follows: (1)The SOD activities of HUC4,OT and HT groups were higher significantly than that of UC group, but the SOD activity of HUC7 declined significantly than that of UC group. When the rats that were exposed to hypoxia was prolonged, their MDA levels maitained higher, but the MDA levels of OT4 and OT7 group were not different than that of UC group. In conclusion, a rise of the SOD activities could counteract the effects of increased free radical generation, or the effects of the latter exceeded the effects of increased antioxidant enzymes. (2)HUC7 and HT7 groups'MCC,MDA concentration ascended, simultaneously their expression of bcl-2 descended, and their apoptotic percentages of the skeletal muscle cells of rats significantly were increased. The double effection of hypoxia and exercise was unable to obviously accelerate the skeletal muscle apoptosis. (3)HUC7 and HT7 groups'apoptosis of the skeletal muscle cells were more than the control group, but these two groups were not different statistically, the results showed the apoptosis were ont increased significantly after hypoxic training, and showed there was a definite relationship between exercise-induced skeletal muscle apoptosis and training load and/or training intensity.The main results of exhausting eccentric exercise groups are as follows: (1)After He and OE groups had exercised, their SOD and MDA entirely showed that they firstly increased, and then decreased in the subsequently different time. In the seven day, their SOD and MDA basically recovered to the normal value, and their total tendency showed that the system of free radical and anti-free radical gradually recovered balance in the seven day. But OE groups'free radical was more easily cleared away. (2)OE and He groups'the changes of MCC were similar to those of MDA, they all significantly increased immediately after eccentric exercise, and reached maximum at 24 hour after eccentric exercise, and began to descrease at 48h after eccentric exercise, basically recovered from 4d to 7d. (3)By observing OE and He groups'different time after eccentric exercise, we found that apoptosis of the skeletal muscle were more than EC significantly at immediately,1d and 2d after eccentric exercise, and reached maximum at 2d after eccentric exercise.(4)He and OE groups activated PCD of the rats' skeletal muscle following eccentric exercise, they perhaps were induced by dysfunction of the calcium ion's homeostasis, and/or by an increase of ROS at post-exercise. (5)The results showed that exercise-induced muscle damage might be initiated by the skeletal muscle apoptosis. It was found that the trends of He and OE groups'changes of the skeletal muscle apoptosis were basically consistent, showing that the process of the skeletal muscle injuries of the rats under hypoxia was consistent with those under the normoxic condition and that hypoxia was unable to obviously accelerate or deepen the skeletal muscle apoptosis following a single bout of high-intensity exercise.