The relationships among igf-1, dna content and protein accumulation
during skeletal muscle hypertrophy.
Adams, G. R., and F. Haddad.
Department of Physiology and Biophysics, University of California,
Irvine CA 92697
APStracts 3:0394A, 1996.
Insulin-like growth factor-1 (IGF-1) is known to have anabolic effects
on skeletal muscle cells. This study examined the time course of
muscle hypertrophy and associated IGF-1 peptide and mRNA expression.
Data were collected at 3, 7, 14 and 28 days following surgical
removal of synergist muscles using both normal (N) and
hypophysectomized (H) animals. Overloading (OL) increased the
plantaris (PLN) mass, myofiber size and protein to body weight ratio
in both groups (NOL & HOL) (P<0.05). Muscle IGF-1 peptide levels
peaked at 3 (NOL), and 7 (HOL) days of OL with maximum 4.1 (NOL) and
6.2 (HOL) fold increases. Increases in muscle IGF-1 preceded the
hypertrophic response. Total DNA content of the OL PLN increased in
both groups. There was a strong, positive, relationship between IGF-1
peptide and DNA content in the OL PLN from both groups. These results
indicate that: 1) the muscles from rats with both normal and severely
depressed systemic levels of IGF-1 respond to functional overload
with an increase in local IGF-1 expression; and 2) this elevated IGF
-1 may be contributing to the hypertrophy response possibly via the
mobilization of satellite cells to provide increases in muscle DNA.
Received 23 April 1996; accepted in final form 13 August 1996.
APS Manuscript Number A390-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996