Altered expression of myosin mrna and protein in rat soleus and
tibialis anterior following reinnervation.
Huey, Kimberly A., and Sue C. Bodine.
Biomedical Sciences Program, UCSD School of Medicine and VA Medical
Center, San Diego, CA 92093-9151
APStracts 3:0233C, 1996.
Myosin heavy chain (MHC) expression was studied in rat soleus and
tibialis anterior (TA) at the mRNA and protein levels following
reinnervation 8 and 32 weeks after sciatic nerve injury. A sciatic
nerve crush or transection injury was produced in the mid-thigh
region of adult, female Sprague-Dawley rats. An RNase protection
assay (RPA) was developed to measure four of the adult MHCs (I, IIa,
IIx, IIb) in a single sample. MHC mRNA and protein were measured and
compared in the same muscles. Eight and 32 weeks following a crush
injury the MHC mRNA profiles were similar to control with the
exception of soleus IIa-MHC and TA IIb-MHC which were significantly
less than control at both time points. In contrast, reinnervation of
the soleus following a sciatic nerve transection injury resulted in a
MHC isoform shift characterized by increases in the relative amounts
of fast myosin (IIa and IIx) and a decrease in slow myosin. As
expected, significant changes first occurred at the mRNA level
followed by changes in protein expression. Thirty-two weeks after
transection injury and repair, the primary MHC mRNA isoform in the
soleus was IIx-MHC. Moreover, at 32 weeks, IIb-MHC mRNA was detected
in 50% of the reinnervated soleus following a transection injury.
Reinnervation of the TA following sciatic nerve transection led to
replacement of the IIb-MHC isoform with IIx-MHC.
Received 12 March 1996; accepted in final form 10 July 1996.
APS Manuscript Number C134-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996