| Sarcopenia is degenerative changing in skeletal muscles associated with aging.It directly results in decreased muscular strength and endurance,damaged balanced capacity, fatigability,frequently falling, even bone fracture acccordingly being a heavy burden to the society and families.To discover the etiological factor and pathogenesis of Sarcopenia, a good many investigators have been engaging in it painstakingly and at the present time it is generally agreed that the changing of intracellular calcium homeostasis in skeletal muscle has closely-linked relationship with Sarcopenia. MG29 is a transmembrane protein which is most lacated in the key position of regulating calcium entry in endomysium.Studies have shown that the content of MG29 in aging skeletal muscles has decreased by 50% compared with the young rats.The normal young rats showed similar features to the old ones in skeletal muscles if were knocked out the gene of MG29.Many evidences have shown that aging skeletal muscle of Sarcopenia can be strengthened funtionally by exercise,especially by resistance exercise.Has MG29 been changed in content via exercising aging body?So far there are no related reports.To discover the correlation among MG29,exercise and aging body,32 Wistar rats in their 16 months were chosen as the subjects of this experiment.They were grouped into 4 randomly.Of the 4 groups,one was control group(CG) and the other 3 were exercise training groups(EG),which were respectively low load group(LG),meium load group(MG) and high load group(HG).Any exercise intervention was not involved in the CG. For the exercise training groups they were exerted interval run training on treadmill with bearing low,medium and high loads separately for 8 weeks. The speed of the the treadmill was set at 15m/s, the slope was 0°. One set of training consisted of running 2 minutes and resting 2 minutes and 6 sets of this continuous training were exerted,one time for every day and 6 times for every week with Sunday resting.All the rats were weighed one time a week , their hair color and mental status were observed every day.The weight of the load for every rat was calculated by the percent of its maximum load and low load amounted to 30% of their maximum load,medium load is 50% and high load is 60%. At the end of the eighth training week and after the last training,the left mid-rectus femoris muscles of the subjects were cut up.Routine frozen sections were maded with HE staining and afterwards an optical microscope was used to watch the histologic morphology determinations.After homogenation,in muscles the content of lipofuscin was assayed by fluorimetry colorimetry, the concentration of calcium was assayed by methylthymol blue colorimetry and MG29 level was assessed by western blot analysis.The obtained dates were collected analysed by software SPSS17.0 and Excel 2003.The results were obtained after the dates within and between groups were compared.Results: (1) After training,the normal mental status of the rats in the EG was obviously better than the CG and their body weight graphes showed that the weight of the rats in the EG firstly increased ,then dropped,and increased again,but the graph of the CG went up all along. (2) Under the optical microscope,the muscle fibers of all the subjects tended to be round shape in varying degrees.They differed in size and arranged in irregular order.There were excessive gaps among the cells which were filled in by white tissues.And there was a tendency for the cell nucleus to be centralization.In the total 4 groups, the above-mentioned features in the CG is the most significant,the HG is in the next place but the fibers in the LG and MG arranged much more tightly than the above two groups. (3) The results of detecting the lipofuscin's content in muscles showed that the LG and the MG contained the least and the HG and the CG were the most and there was no significant difference between the the LG and the MG,as well as between the HG and the CG.(4) The results of detecting the concentration of calcium showed that the LG was on the toppest and had significant difference when compared with the other 3. And the CG had the least apparently but there was no significant difference between the MG and the HG. (5) MG29 level in the muscles was detected by western blotting, the analysing results of the electrophoretogram showed that the MG29 level in the LG is remarkably elevated.The MG ranked the second and the next is CG,the last is HG.Compared with the other 3 groups,they all had significant difference.Conclusions:(1)The study shows that motor stimulation of proper exercise intensity can effectively elevate the MG29 level in the skeletal muscles of rats, improve the structure and functions of the fibers, thus lessen the muscular atrophy and lost during aging and delay the process of Sarcopenia.(2)30% and 50% maximum load of interval load-bearing running may be a proper motor stimulation for delaying the aging process of skeletal muscles in rats. It can elevate the MG29 level in skeletal muscles effectively, consequently keep the normal structures of excitation contraction coupling,thus promote extracellular calcium entry,and hold even boost up the functions of skeletal muscles. As a result, the free radicals in fibers reduce relatively, muscular atrophy and lost decreases , and it happens that the process of sarcopenia delays.(3)Maybe 60% maximum load of interval load-bearing running is not a proper motor stimulation for aging skeletal musle in rats, for under this motor stimulation the MG29 level falls significantly, thus the functions of skeletal muscles shrink greatly, and the free radical level rise apparently, the cummulation of lipofusion grows largely. Therefore, this motor stimulation may accelerate the process of sarcopenia.
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