The Influence Of Overloading On The Catabolism Of Protein And The Gene Expression Of Myogenic Regulatory Factors In The Skeletal Muscles Of Male Rats

Objective: The purpose of this study is to investigate the effects of overloading on the gene expression of Myogenic Regulatory Factors (MRFs) in the skeletal muscles of male Spraque-Dawley (SD) rats.Methods:20 SD male rats that only 6 weeks old were randomly divided into 2 groups: A, control group(C,n=10);B, overloading group(OL,n=10). Form the second week on, the rats of the heavy-load training group carried out continuous uphill running with the speed from 15m/min to 40m/min(+5m/5min) for 60 min a day. The training was continued for 8 weeks (six days for training ,one day for resting each week). The rats were fed in different chambers taking food and drinking freely. The rats of two groups were all killed and the samples of quadriceps were collected immediately and stored in liquid nitrogen. The composition of the contraction proteins was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The skeletal muscle cathepsin D activity was measured by means of ultraviolet spectroscopy, the gene expression of MyoD and Myog mRNA were determined by using realtime-polymerase chain reaction(RealTime-PCR).Result: 1) After the SDS-PAGE of skeletal muscle contraction protein, a large number of new strips appeared in the collection of illustrative plates in OT group. The range of molecular weight was 43 ~ 200 kDa.2)After 8 weeks'overloading, the skeletal muscle cathepsin D activity of overloading group is significant higher than that of control group. 3)The result of RealTime PCR showed that, the gene expression of MyoD of overloading group was decreased significantly compared with the base contrast group(P<0.05). Mean while ,the expression of Myog had a trend to decrease. (P>0.05)Conclusion: In this training pattern, after the SDS-PAGE of the skeletal muscle contraction protein, a large number of new strips appeared in the collection of illustrative plates in overloading group. Meanwhile, the skeletal muscle cathepsin D activity of overloading group was significant higher than control group. It showed that the catabolism level of skeletal muscle contraction protein was significantly increased than before, and it maybe have some relations with new strips which appeared in the collection of illustrative plates. The results of RealTime-PCR showed that the gene expression of Myod mRNA of overloading group was significant decreased compared with the control group, and the expression of Myog mRNA had a trend to decrease. It point out that overloading cannot promote the gene expression of MRFs mRNA .The changes of MRFs in protein level needs a further observation.