Selective regulation of myofiber hypertrophy and differentiation by
energy status during postnatal development .
Harrison, A. P., A. M. Rowlerson, and M. J. Dauncey.
Department of Cellular Physiology, The Babraham Institute,
Cambridge, CB2 4AT; and Division of Physiology, U.M.D.S. St Thomas's
Hospital, University of London SE1 7EH, United Kingdom
APStracts 2:0286R, 1995.
The role of energy status in postnatal regulation of porcine skeletal
muscle development has been determined in littermate animals kept for
3-4 weeks on a high (H) or low (L) energy intake (H=2L), at a
thermally neutral (26oC) or low (10oC) environmental temperature. A
variety of skeletal muscles was assessed at 7 weeks of age for
changes in myofiber hypertrophy and differentiation. By contrast with
findings in adult humans and rats there was no selective preservation
of type I slow-oxidative fiber size during energy restriction.
However, differentiation between mature skeletal myosin heavy chain
isoforms was markedly affected by energy status, and in rhomboideus
there were particularly striking effects of both nutrition and
temperature: proportions of type I fibers from the four groups 26H,
26L, 10H and 10L were 34 +/- 2, 50 +/- 4, 73 +/- 2 and 72 +/- 3
(P<0.005 for diet at 26oC; P<0.001 for temperature). These
changes may have been induced by alterations in both thyroid status
and contractile activity. They support the hypothesis of a key role
for rhomboideus muscle in thermoregulation and demonstrate the
plasticity of skeletal muscle differentiation to environmental change
during postnatal life.
Received 13 April 1995; accepted in final form 18 October 1995.
APS Manuscript Number R238-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 November 95