AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 5 880-R883, Copyright © 1984 by American Physiological Society
Glycogen resynthesis in leg muscles of rats during exercise
S. H. Constable, J. C. Young, M. Higuchi and J. O. Holloszy
This study was undertaken to determine whether glycogen resynthesis can
occur in glycogen-depleted muscles in response to glucose feeding during
prolonged exercise. Rats were exercised for 40 min with a treadmill running
program designed to deplete muscle glycogen. One group was studied
immediately after the glycogen-depletion exercise. A second group was given
1 g glucose by stomach tube and exercised for an additional 90 min at a
running speed of 22 m/min on a treadmill set at an 8 degree incline; they
were given additional 1-g glucose feedings after 30 and 60 min of running.
The initial 40-min run resulted in liver glycogen depletion, large
decreases in plasma glucose and insulin concentrations, and a marked
lowering of muscle glycogen. The glucose feedings resulted in greater than
twofold increases in the concentrations of glucose and insulin in plasma,
and of glycogen in leg muscles, during the 90 min of running. No repletion
of liver glycogen occurred. These results provide evidence that glycogen
resynthesis can occur in glycogen-depleted muscle despite continued
moderate intensity exercise if sufficient glucose is made available.
