AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 3 353-R356, Copyright © 1983 by American Physiological Society
Glycogenolytic rates and cAMP in livers of rats running at different treadmill speeds
W. W. Winder, M. A. Beattie and E. O. Fuller
The purposes of this study were to determine the effect of different work
rates on the rate of liver glycogenolysis and to determine the relationship
between liver adenosine 3',5'-cyclic monophosphate (cAMP) levels and the
glycogenolytic rate. Rats were run at treadmill speeds ranging from 10 to
34 m/min up a 15% grade for either 30 or 60 min. Both the magnitude of the
decrease in liver glycogen and the increase in hepatic cAMP were dependent
on the running speed and the duration of running. At the highest work rate
a disproportionate acceleration in the liver glycogenolytic rate was
observed compared with that at lower work loads, thus resulting in a
curvilinear relationship between work rate and liver glycogenolytic rate. A
high degree of correlation was found between the liver glycogenolytic rate
and hepatic cAMP concentration (r = 0.98). This observation is consistent
with the idea that hepatic glycogenolytic rates are determined by
cAMP-mediated mechanisms.
