Cytoskeletal protein contents before and after hindlimb suspension in a fast and slow rat skeletal muscle

Transversal cytoskeletal organization of muscle fibers is well described, a lthough very few data are available concerning protein content. Measurement s of desmin, alpha -actinin, and actin contents in soleus and extensor digi torum longus (EDL) rat skeletal muscles, taken with the results previously reported for several dystrophin-glycoprotein complex (DGC) components, indi cate that the contents of most cytoskeletal proteins are higher in slow-typ e fibers than in fast ones. The effects of hypokinesia and unloading on the cytoskeleton were also investigated, using hindlimb suspension. First, thi s resulted in a decrease in contractile protein contents, only after 6 wk, in the soleus. Dystrophin and associated proteins were shown to be reduced for soleus at 3 wk, whereas only the dystrophin-associated proteins were fo und to increase after 6 wk. On the other hand, the contents of DGC componen ts were increased for EDL for the two durations. Desmin and alpha -actinin levels were unchanged in the same conditions. Consequently, it can be concl uded that the cytoskeletal protein expression levels could largely contribu te to muscle fiber adaptation induced by modified functional demands.