Effect of chronic denervation and denervation-reinnervation on cytoplasmiccreatine kinase transcript accumulation

The extensor digitorum longus (F,DI,) and soleus muscles of adult mice were chronically denervated or denervated and allowed to reinnervate, Muscles w ere evaluated 1, 5, 14, 21, and 52 days after sciaticectomy. In terms of we ight loss, myofiber atrophy, degeneration, and fibrosis, the soleus muscle was more affected than the EDL by chronic denervation, Fifty-two days after chronic denervation, the number of molecules of MCK/ng total RNA in both m uscles (determined with competitive PCR) decreased, with the soleus muscle being more affected. At that stage, BCK mRNA levels in the denervated soleu s were unchanged, but they were increased (> 50%) in the EDL, Reinnervation restored MCK transcript accumulation in the EDL, whereas, in the soleus MC K, transcripts exceeded control values by 57%, approaching levels in the re innervated EDL. Despite restoration of MCK mRNA levels, the number of molec ules of BCK mRNA/ng total RNA was four- to fivefold higher in reinnervated versus control muscles, suggesting that the genes encoding the CK mRNAs are not coordinately regulated in adult muscle. The role of denervation induce d, fiber type changes in regulating CK mRNA accumulation has been evaluated . Electron microscopic analyses ha c e established that fibrosis is not a f actor that determines BCK mRNA levels in the chronically denervated or dene rvated-reinnervated muscles. CK isozyme analyses support the hypothesis tha t a greater proportion of BCK mRNA found in 52 day chronically denervated a nd denervated-reinnervated muscles is produced in myofibers vs, nonmuscle c ells than in control muscles, (C) 2001 John Wiley & Sons, Inc.