Regulation of succinate dehydrogenase within muscle fiber
compartments by nerve-mediated activity and cntf.
Michel, Robin N., Robert J. Campbell, and Bernard J. Jasmin.
Neuromuscular Research Laboratory, Department of Chemistry and
Biochemistry, Laurentian University, Ramsey Lake Road, Sudbury,
Ontario, Canada P3E 2C6
APStracts 2:0195R, 1995.
We investigated the regulatory effects of neural activation and
trophic factors on the selective accumulation of succinate
dehydrogenase (SDH; EC 1.3.99.1) activity at the endplate, as well as
within subsarcolemmal and intermyofibrillar regions of rat soleus
muscle fibers. The role of activation was assessed by stimulating
tetrodotoxin (TTX)-inactivated nerves distal to the site of drug
application. We also studied whether ciliary neurotrophic factor
(CNTF) is involved in regulating the postsynaptic accumulation of
SDH. Using quantitative microphotometry, we found that daily
stimulation of quiescent but intact nerves prevented the TTX-induced
decrease in SDH activity within extrajunctional regions, whereas at
the endplate, the counteraction was partial (30%). Thus, it appears
that endplate levels of this enzyme are regulated by a complex
mechanism involving an interaction between neuromuscular activation
and trophic factors. We also found that daily CNTF administration
counteracted the denervation-associated loss of SDH activity
exclusively within the intermyofibrillar compartment, suggesting that
CNTF treatment mimics the effects of activity on SDH levels within
the core region of denervated fibers, but under these conditions does
not influence the endplate accumulation of this enzyme.
Received 16 March 1995; accepted in final form 3 July 1995.
APS Manuscript Number R179-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.