Induction of neuronal type nitric oxide synthase in skeletal muscle
by chronic electrical stimulation in vivo.
Reiser, Peter J., William O. Kline and Pal L. Vaghy.
Departments of Oral Biology, Exercise Science and Medical
Biochemistry, The Ohio State University, Columbus, Ohio 43210
APStracts 3:0553A, 1996.
Fast-twitch skeletal muscles contain more neuronal type nitric oxide
synthase (nNOS) than slow-twitch muscles because nNOS is present only
in fast (type II) muscle fibers. Chronic in vivo electrical
stimulation of tibialis anterior and extensor digitorum longus
muscles of rabbits was used as a method of inducing fast-to-slow
fiber type transformation. We have studied if an increase in muscle
contractile activity induced by electrical stimulation alters nNOS
expression, and if so, does the nNOS expression decrease to the
levels present in slow muscles. Changes in the expression of myosin
heavy chain isoforms and maximum velocity of shortening of skinned
fibers indicated characteristic fast-to-slow fiber type
transformation after three weeks of stimulation. At the same time,
activity of NOS doubled in the stimulated muscles and this correlated
with an increase in the expression of nNOS shown by immunoblot
analysis. These data suggest that nNOS expression in skeletal muscle
is regulated by muscle activity and this regulation does not
necessarily follow the fast-twitch and slow-twitch pattern during the
dynamic phase of phenotype transformation.
Received 15 March 1996; accepted in final form 20 November 1996.
APS Manuscript Number A264-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996