Glycogen supercompensation in rat soleus muscle during recovery from nonweight bearing

Events leading to the normalization of the glycogen metabolism in the soleus muscle of rat, altered by 72-h three days of hind-limb suspension, were investigated during the 72-h recovery period when the animals were allowed to bear weight on all four limbs. Relative importance of the factors affecting glycogen metabolism in skeletal muscle during the recovery period was also examined. Glycogen concentration was found to decrease within 15 min and up to 2 h of recovery, while muscle glucose 6-phosphate, and the fractional activities of glycogen phosphorylase and glycogen synthase increased. From 2 to 4 h, when the glycogen synthase activity remained elevated and the phosphorylase activity declined, glycogen concentration increased, until it reached maximum values at about 24 h, after which it started to decrease, reaching control values by 72 h. At 12 and 24 h, the inverse relationship between glycogen concentration and the synthase activity ratio was lost, indicating that the reloading transiently uncoupled glycogen control of this enzyme.