Skeletal and cardiac muscle protein turnover during short-term cold
exposure and rewarming in young rats.
Samuels, S. E., J. R. Thompson, and R. J. Christopherson.
Department of Agricultural, Food and Nutritional Science,
University of Alberta, Edmonton, Alberta, Canada T6G 2P5
APStracts 3:0017R, 1996.
Young animals exposed to cold environmental temperatures typically
have decreased skeletal muscle accretion, but increased heart masses.
To explore these phenomena, we measured protein synthesis and
degradation in vivo in cardiac and skeletal muscle in weanling rats
during short-term cold exposure and rewarming. Control rats were
housed at 25oC throughout the experiment. Ad libitum-fed and pair-fed
(to the intake of controls) rats were housed at 5oC (cold) for 5 d
and then at 25oC (rewarmed) for another 5 d. Cold exposure decreased
rates of protein accretion and synthesis in skeletal muscle, while
degradation did not differ. The effects of cold exposure on skeletal
muscle were similar in both pair-fed and ad libitum-fed rats, except
growth was lower in pair-fed rats. In cardiac muscle, cold exposure
increased rates of protein synthesis and degradation and resulted in
increased cardiac mass. Results in pair-fed animals generally fell
between those of control and ad libitum-fed cold rats. During
rewarming, growth rates were not higher in skeletal muscle in ad
libitum-fed rewarmed rats although protein turnover returned toward
control values; in pair-fed rats, it remained lower. In heart, growth
rates of ad libitum-fed and pair-fed rewarmed rats decreased due to
lower protein synthesis rates. These alterations appear to be
consistant with a strategy designed to improve survival in cold
environments.
Received 12 June 195; accepted in final form 11 December 1995.
APS Manuscript Number R354-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96