Induction of a fast-oxidative phenotype by chronic stimulation of
muscle: mechanical and biochemical studies.
Jarvis, Jonathan C., Hazel Sutherland, Caroline N. Mayne, Stephen J.
Gilroy, and Stanley Salmons.
Department of Human Anatomy and Cell Biology, The University of
Liverpool, P.O. Box 147, Liverpool L69 3BX, U.K.
APStracts 2:0285C, 1995.
We studied changes in the mechanical properties and myosin isoform
composition of rabbit tibialis anterior muscles that were subjected
to continuous stimulation at 2.5 Hz for up to 12 weeks. The effects
of stimulation at 2.5 Hz were less profound than those observed for
the same duration of stimulation at 10_Hz (12). Stimulation at 10_Hz
for 12_weeks induced complete transformation to a slow-contracting
muscle homogeneous in slow myosin isoforms; stimulation for the same
period at 2.5 Hz resulted in moderate changes in contractile speed
and a very small increase in the synthesis of slow myosin isoforms.
On the other hand the fatigue resistance of muscles stimulated at 2.5
Hz was as great, in both isometric and dynamic fatigue tests, as that
of the muscles stimulated at 10 Hz. Thus entire fast skeletal muscles
can be transformed to a state in which fast myosin isoforms continue
to be synthesized but the oxidative capacity is sufficient to support
sustained working at a higher power output than that associated with
slow muscle.
Received 21 November 1994; accepted in final form 10 July 1995.
APS Manuscript Number C686-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 August 1995.