| Objective:The purpose of this study is to investigate the changes of ultrastructure and mechanical growth factor in skeletal muscle during recovery period after one-time exhaustive exercise in rats.Method:(part one):24SD adult rats that only7weeks old were randomly divided in to4groups, and each group had six rats. Control group(C),Immediately after exhaustive exercise group(EO),24hours after exhaustive exercise group(E24),48hours after exhaustive exercise group(E48). All exhaustive exercise groups were carried on one-time exhaustive exercise at different time points, each rat was anesthetized intraperitoneally to Slaughter with Urethane, and the vastus lateralis, rectus femoris muscle were taken. Some were used for cryopreservation in Liquid nitrogen and the others were used to fix with4%paraformaldehyde or2.5%glutaraldehyde. The Protein expression of Mechano growth factor were measured by ELISA.(part two):4SD adult were processed as follow:one as Control, one as immediately group after blunt trauma, one as24hours group after blunt trauma, one as48hours group after blunt trauma, and another neonatal rat group. All group were taken the vastus lateralis muscle at different time points and immediately used for culture of muscle satellite cell, then observed by inverted phase-contrast microscope.Result:(1) In control group, the rectus femoris muscle ultra structure in rats was detected under electron microscope with a integrated myofibril structure and the normal endoplasmic reticulum and mitochondria boundary. H belt, I belt, M line, Z line and nucleus were clear. After exhaustive exercise skeletal muscle ultrastructure changed with a deformed mitochondria, endoplasmic reticulum and the ill-defined myofibril, M line and Z line not clear enough, and H belt and I belt blured. After exhaustive exercise immediately, there were inflammatory cell infiltration and stromal vascular changes. Then after exhaustive exercise in24hours, the skeletal muscle fibre transformed and mitochondria deformed and enlarged. Z line were distorted and cristal has disturbance. (2) ELISA results showed that compared with the control group, the contents of MGF in serum from exhaustive exercise groups EO, E24, E48were very significantly increased (P<0.01). On the other hand, the contents of MGF in skeletal muscle from EO, E24, E48were also increased compared with control group, and there was a significant difference between the control group and E24group (P<0.01).(3) In the control group, the skeletal muscle satellite cells was initially rounded and suspended in culture medium. After one days’growth of adherent cells, the cells are small and round with an uniform distribution. Then the cells enlarged and began to split, and3-5or a plurality of cells in clusters can be seen by microscope. The number of muscle satellite cells of neonatal rat in culture were more than that of adult rat. Muscle satellite cell in adherent culture for48hours can be observed to cell proliferation with a rapid proliferation in the5-8days, then slow down.Conclusion:(1) The results by electron microscopy showed that:a single bout of exhaustive exercise can cause the ultrastructure changes of skeletal muscle in rats:Z lines was irregular. Endoplasmic reticulum and mitochondria obscured. Myofibril deranged and cell interstitial occured edema. Muscle gap widened and so on.(2) The levels of mechanical growth factor in rats’serum and skeletal muscle were an increasing trend at24hours and48hours after exhaustive exercise with a peak in24hours. It indicated that the mechano growth factor may be an important role of microvascular repair and tissue regeneration and repair.(3) The culture in vitro of satellite cells in rat skeletal muscle needs many requirements. The proliferation ability of satellite cell in skeletal muscle after blunt trauma was stronger than that of control group. And the satellite cell proliferation of neonatal rat was stronger than that of adult rat. |
