Large Load Exercise And During Recovery In Rat Skeletal Muscle Ultrastructure And Changes In The Fibroblast Growth Factor

Objective:The purpose of this paper was to study the changes of skeletal muscle ultrasructure and fibroblast growth factor(FGF) during heavy load exercise and recovery in rat.Methods:36 male SD rats of 6-week-old were randomly divided into 6 groups:control group, (control,C)and after exhaustive exercise group (Exhaustiive,E0),12h group(E12),24hgroup(E24), 48h group(E48),72h group(E72).Movement pattern of rat was tail-loaded swimming with the weight of 3%of body weight.Rats in exercise group separately carried on a no-load adapting swimming for three days.Then the rats of exercise groups carried on exhaustive loaded swimming every day for one week.After 2%peritoneal sodium pentobarbital anesthesia by an intraperitoneal injection,5ml blood sample was taken from the abdominal aorta at different recovery time.The serum was used to measure the fibroblast growth factor contents. A side of the rectus femoris muscle sample was fixed for producing ultrathin sections by transmission electron microscope observation of the ultrastructural changes.The other side of one was reserved in liquid nitrogen to measure the fibroblast growth factor contents.Results:1)By observing the electron micrographs of the rectus femoris,we found a normal ultrastructure of skeletal muscle in the control group. The endoplasmic reticulum and mitochondria were clearly visible.The nuclei showed normal structure.The myofibril arranged regular, and the H band,I band,M line and Z line of the boundaries were clear.There are only few vacuole matrix. On the other hand the skeletal muscle structure in exhaustive exercise groups (E0,E24) were significantly damaged with an interstitial edema, and muscle gap widened. The endoplasmic reticulum and mitochondria were slightly deformed.The nucleus and nuclear membrane preserved also;The myofibril become thinner and more incompact.H band and I band took ill-defined.M lines and Z lines blurred.Z lines were distorted and disappeared.Some matrix become shallow,and mitochondrials were deformed,distorted and swollen.2)After a week of exhaustive swimming,serum FGF contents increased significantly in the groups of E12 and E24 compared with the quiet control group,(P<0.05),(P<0.01).On the other hand FGF contents in the skeletal muscles also increased significantly in the groups of E0,E12, E24,E48 and E72 compared with the quiet control group (P<0.05),(P<0.01).Conclusions:1)The ultrastructure of muscle fiber changed and become unclear during heavy load exercise and recovery.The structure of endoplasmic reticulum and mitochondria blurred.The cristae increased and disordered, or even disappeared.The muscle gap widened with an interstitial edema.2)The FGF contents in the skeletal muscles also increased significantly during heavy load exercise and recovery with a peak at E24.It indicated that fibroblast growth factor maybe accele-rated the repair of soft tissue injury.3)The serum FGF contents showed a rising trend during heavy load exercise and recovery, especially in E12 and E24.It indicated that fibroblast growth factor may be one of the indexes which accelerated the repair of organizations and microvasculars.