Journal of Applied Physiology, Vol 58, Issue 1 211-216, Copyright © 1985 by American Physiological Society
Effect of cold exposure on liver and muscle cAMP content and cAMP phosphodiesterase activity
W. K. Palmer, T. A. Kane, F. Bach and S. Doukas
Adenosine 3',5'-cyclic monophosphate (cAMP) concentration and
3',5'-cyclic-nucleotide phosphodiesterase (PDE) activity were measured in
skeletal muscle, heart, and liver of rats exposed to 1, 3, 5, and 7 days of
cold. Cyclic nucleotide concentration increased in fast-twitch red muscle
at the same time that PDE activity was decreasing. Nucleotide concentration
and enzyme activity of slow-twitch red muscle were not altered by the cold
exposure. The PDE activity of fast-twitch white muscle was elevated
approximately 50% above control after 1 and 3 days of cold exposure. By the
5th day in the cold, white muscle PDE activity had returned to control
levels and remained there through the 7th day of experimentation. cAMP
concentration in hearts of cold-exposed rats was significantly (P less than
0.01) elevated above control at all time points measured. Myocardial PDE
activity was elevated above control (P less than 0.05) at 1 and 3 days of
cold exposure but returned to control levels by the 5th day in the cold.
Hepatic cAMP and PDE activity were elevated above control at all time
points analyzed. These data suggest that changes in cyclic nucleotide
metabolism play a role in attaining homeostasis during acute cold exposure.
