The Influences Of Tail Suspension And Angiotensin â…¡ To The Transformation Of Muscle Fiber Type And Moter End Plate

Objective:to study how tail suspension and angiotensin II affect the transformation of skeletal muscle fiber type and the motor end plate.Method:32 female SD rats were randomly divided into four groups:control group (C), control group with slow-pumped angiotensinâ…¡(CA), tail-suspension group for 2 weeks (T),2 weeks'tail-suspension with slow-pumped angiotensin II group (TA); 8 rats for each group. Use metachromatic dye-ATPase stain method to stain gastrocnemius frozen section for different fiber types, to count the changes of muscle fiber type; Use AuC13 staining method and AchE staining method to stain motor end plate, to observe the changes of motor end plate; Use western blot method to observe the expression of NT-3 protein.Results:(1) Metachromatic dye-ATPase staining shows that, compared with group C, typeâ… muscle fiber of group T decreased significantly(p<0.01), while typeâ…¡muscle fiber increased significantly, and group CA had no significant difference with group C; (2) After AuC13 staining, compared with group C, the area of motor end plate of group T decreased significantly (p<0.01); compared with gourp T, the area of group TA had a significant increase; (3) After AchE staining, compared with group C, the IOD of AchE in group T decreased significantly(p<0.01); while compared with gourp T, the IOD in group TA had a significant increase; (4) The expression of protein NT-3:compared with group C, goup CA had a significantly higher expression of NT-3, while the NT-3 expression of group T decreased significantly; compared with group T, the NT-3 expression of group TA increased significantly.Conclusions:(1) The disuse atrophy caused by tail suspension can cause the muscle fibers to transform from slow fibers to fast fibers, while Angâ…¡can hold up the process; (2) After tail suspension, the motor end plate degenerated, and AchE decreased, Angâ…¡can hold the proccess and protect the motor end plate; (3) Tail suspension cause NT-3 expression to decrease, while Angâ…¡promote the expression of NT-3.