Experimental Study On Endogenous Cells Growth Factor In Rat's Exercise-induced Skeletal Muscle Damage

Background: The training effect lies on the equilibrium of the two facets. Presently, the domestic study of skeletal muscle exercise damage is rarely done which is mainly localized in the study of exercise effect to the ultrastructure, bio-chemistry and enzymology in the skeletal muscle. Overseas study of cell factors expression in exercise-induced skeletal muscle damage is in the initial phase. The regeneration of skeletal muscle which is followed by complicated biological regulative mechanism is relative to many cell factors. Thereinto the cell factor insulin-like growth factor(IGF) is concerned with cell proliferation and differentiation in the rehabilitation for skeletal muscle damage. IGF-â… chiefly promotes the cell proliferation of skeletal muscle, while IGF-â…¡is vital in the differentication of the proliferated skeletal muscle cells. Otherwise, basic fibroblast growth factor (bFGF) is the primary growth factor in the regulation of skeletal muscle embryogenesis, growth and development which is potent regulator in skeletal muscle proliferation and differentiation. Cell apoptosis is an important factor in the cell necrose following the skeletal muscle damage. The apoptosis relative genes such as Bcl-2, Bax are crucial in skeletal muscle cell spoptosis. Adaptation and damage are two dichotomal facets in daily physical exercise and military training.Objective: To investigate the expression of endogenous cytokine in different time with exercise-induced skeletal muscle damage, and the relationship between the cytokines with apoptosis,necrosis,regeneration of skeletal muscle cells. To provide fundamental theory for the study of the pathogenesis, preventive and therapy of exercise-induced skeletal muscle damage.Methods: Different grades of animal modles of rat exerise-induced skeletal muscle damage were made. The pair of gastrocnemius muscles of rats which suffered from exerise-induced damage were dissected. Electron microscope was used to observe their ultrastructure and flow cytometer was used to detect the apoptosis of skeletal muscle cells in different damage phases. Reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate the amount of insulin-like growth factor mRNA in exercise-induced damaged skeletal muscle.Results: 1. mRNA of IGF: a The amount of skeletal muscle endogenous IGF-â… andâ…¡mRNA were not changed in contrast groupe which SD rats were not exercised, b. The amount of skeletal muscle endogenous IGF-â… mRNA was increased from begining in normal exercised group, Its level reached the summit at the 10th day, and it began to decrease at the 17th day; The amount of endogenous IGF-â…¡mRNA began to increase at the 7th day in normal exercised group, and it reached the summit during the 13th to 17th day. c. The amount of endogenous IGF-â… rnRNA began to increase from the begining in one-week-exhausting-exercised group, it reached the summit at the 7th day, and it began to decrease at the 13th day; The amount of endogenous IGF-â…¡mRNA began to increase at the 4th day in one-week-exhausting-exercised group, and it reached the summit at the 10th day which was maintained for several days. 2. mRNA of bFGF: The endogenous bFGF mRNA in skeletal muscle cells was almost not expressed in control group whose SD rats were not exercised. It was not expressed in normal training condition, and not expressed in the one-week-exhausting-exercisedgroup, too. 3. Ultrastructure: ultrastrucmre shows that the skeletal muscles of exhausting-exercised group were most badly damaged and the muscles of the other groups were damaged at various levels. 4. Apoptosis: the expressed rnRNA amount of bcl-2 in gastrocnemius muscles of one-week-exhausting-exercised group is significantly higher than that of other groups, and similary change tendency exits in other groups. The expression of Bax appears the opposite tendency, while similary phynomena appeared in other groups.Conclusion: 1. Endogenous insulin-like growth factorâ… andâ…¡mRNA were expressed during regeneration following skeletal muscle contusion and related to the rehabilitation process. 2. Apoptosis appears in the procession of skeletal muscle exercise-induced damage and the phenomenon of apoptosis is proportionally obvious with the damage level.