AJP - Cell Physiology, Vol 262, Issue 6 C1471-C1477, Copyright © 1992 by American Physiological Society
Glucocorticoid-induced skeletal muscle atrophy in vitro is attenuated by mechanical stimulation
J. A. Chromiak and H. H. Vandenburgh
Department of Pathology, Brown University, Providence, Rhode Island.
Glucocorticoids induce rapid atrophy of fast skeletal myofibers in vivo,
and either weight lifting or endurance exercise reduces this atrophy by
unknown mechanisms. We examined the effects of the synthetic glucocorticoid
dexamethasone (Dex) on protein turnover in tissue-cultured avian fast
skeletal myofibers and determined whether repetitive mechanical stretch
altered the myofiber response to Dex. In static cultures after 3-5 days,
10(-8) M Dex decreased total protein content 42-74%, total protein
synthesis rates 38-56%, mean myofiber diameter 35%, myosin heavy chain
(MHC) content 86%, MHC synthesis rate 44%, and fibronectin synthesis rate
29%. Repetitive 10% stretch-relaxations of the cultured myofibers for 60 s
every 5 min for 3-4 days prevented 52% of the Dex-induced decrease in
protein content, 42% of the decrease in total protein synthesis rate, 77%
of the decrease in MHC content, 42% of the decrease in MHC synthesis rate,
and 67% of the decrease in fibronectin synthesis rate. This in vitro model
system will complement in vivo studies in understanding the mechanism by
which mechanical activity and glucocorticoids interact to regulate skeletal
muscle growth.
