| Objective: As the endogenous defense system and the signaling pathway of disease incidence, Endoplasmic reticulum stress (ERS) has important physiological and pathological significance. During the process of exercise-induced muscle injury, there will be different levels of oxidative stress. However, whether oxidative stress will cause ERS is currently unknown. Therefore, this paper aims to discuss the changes of ERS and provide new views to discuss the mechanism of EIMD as well as the promotion of injury repair.Methods: 72 8-week-old healthy male SD rats were randomly divided into control group and exercise group. The exercise group were sub-divided into 0h after the exercise group, 6h after exercise group, 12h after exercise group, 1d after exercise group, 2d after exercise group, 3d after exercise group, 1w after exercise group and 2w after exercise group respectively(n = 8). When it comes to the formal experiment, all animals were designed to take a bout of acute exercise of downhill running at a speed of 16m/min with a gradient of -16°and the total exercise time is 90min. After exercise, the rats were killed in 0h, 6h, 12h, 1d, 2d, 3d, 1w, 2w respectively. Histological examination of the right gastrocnemius of the rats were completed by conventional HE staining; the assay of the endoplasmic reticulum stress protein were taken by western blot, and at the same time SOD and MDA changes were measured. The acquisition and analysis of images were taken through Photoshop and Scion Image analysis software. Data was analyzed by the use of SPSS17.0 statistical software.Results : (1) the histological results showed: muscle cells of control group are arranged in neat rows and rules, no significant morphological changes were found in 0h after the exercise group; swelling muscle fiber were found in 6h; there were continuous swelling muscle fibers in 12h; rupture of part of the muscle fibers exits in1d after exercise group; inflammatory cells increased obviously in 2d; inflammatory cell infiltration were found in 3d ,In addition 3d were confronted with the most serious damage; infiltration of inflammatory cells can still be observed in 1w; morphology of the muscle fibers returned to normal on the whole in 2w ; (2) the changes of SOD in exercise group indicated: the content of SOD reached peak immediately after the exercise and then decreased in each group while the 1 d,3d and the 2w group decreased to the lowest value. Changes in MDA were presented as follows: the content of MDA reached a peak immediately after exercise and subsequently decreased in each group while the group of 2w after exercise was lower than the control group. SOD/MDA as a whole decreased and then increased while the 1d after exercise group reached the lowest value and the exercise group were lower than the control group; (3) Changes of GRP78 and GADD153 as well as the ratio of GRP78/GADD153 in each exercise group were presented as follows: The expression of GRP78 and GADD153 continued to increase after exercise, the ratio of GRP78/GADD153 rose too. However, the 2d group decrease, and then the 3d and 1w group continued to increase while the 3w group began to drop, but it was still higher than the control group.Conclusion: (1) SOD/MDA as a whole decreased and then increased while the 1d after exercise group reached the lowest value ,the changes of SOD/MDA in exercise group indicated that during the early period of skeletal muscle injury and repair, the antioxidant capacity continued to decline and the expression of ERS protein continued to increase which indicates that the ERS was caused by the oxidative stress; (2) Changes of GRP78 and GADD153 as well as the ratio of GRP78/GADD153 in each exercise group were presented as follows: The expression of GRP78 and GADD153 continued to increase after exercise, the ratio of GRP78/GADD153 rose too. However, the 2d group decrease, and then the 3d and 1w group continued to increase while the 3w group began to drop. Combining histological changes ,it indicated that in the late period of the skeletal muscle repair, ERS may play a positive role in the repair of skeletal muscle injury.
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