ROLE OF AFFERENT INPUT AND MECHANICAL LOAD FOR SIZE REGULATION OFRAT SOLEUS MUSCLE

摘要

Effects of deafferentation on the phosphorylation ofrnribosomal protein S6 (S6), 27 kDa heat shock proteinrn(HSP27) and extracellular signal-regulated kinase (ERK)rn1/2 were studied in rat soleus muscle. Adult malernWistar rats were randomly separated into the pre- andrnpost- experimental control, functionally overloaded (FO),rnsham-operated, deafferentated (DA), FO+DA, andrnhindlimb -unloaded (U) groups. The distal tendons ofrnleft plantaris and gastrocnemius muscles were transectedrnin the FO rats. The left dorsal roots of the spinal cord atrnthe L4-5 segmental levels were transected in the DA rats.rnThe rats in U were tail-suspended. The sampling of thernsoleus muscle was performed 2 weeks after the treatmentsrnshown above. The cytoplasmic fraction of the soleusrnmuscle homogenate was used for the quantitativernanalyses of the phosphorylation levels of S6, HSP27, andrnERK 1/2. The phosphorylation levels of these proteinsrnwere up-regulated by FO. On the contrary, thernphosphorylation of all of these proteins wasrndown-regulated by U and DA. Further, the FO-relatedrnincrease of the protein phosphorylation was inhibited byrnadditional treatment with DA. These results indicatedrnthat the afferent feedback plays crucial roles in thernintramuscular regulation of the soleus muscle mass.