AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 3 552-R559, Copyright © 1986 by American Physiological Society
Effect of adrenodemedullation on metabolic responses to high-intensity exercise
J. C. Marker, D. A. Arnall, R. K. Conlee and W. W. Winder
To determine the role of epinephrine in glycogenolysis during
high-intensity exercise, rats were adrenodemedullated (ADM) or sham
operated (SHAM) and run for either 30 min at 38 m/min or for 5 min at 27,
38, or 48 m/min up a 15% grade. At the end of exercise the rats were
anesthetized by intravenous injection of pentobarbital sodium. Liver,
blood, and muscle samples were obtained. Plasma epinephrine values were 5.9
and 0.3 nM for SHAM and ADM animals, respectively, after 30 min of
exercise. Liver glycogen decreased by 16 and 21 mg/g in the SHAM and ADM
groups, respectively, and liver cAMP increased significantly in both
groups. Glycogen in the soleus muscle decreased 80% in the SHAM but only
43% in the ADM animals after 30 min of exercise. The exercise-induced
hyperglycemia observed in the SHAM animals was not present in the ADM
animals. The responses of cyclic AMP, soleus glycogen, and blood glucose
were similar in both the 5- and 30-min exercise groups. During intense
exercise, epinephrine is unessential for stimulating liver glycogenolysis
but does play an important role in stimulating glycogenolysis in the soleus
muscle and in establishing exercise-induced hyperglycemia.
