Glycogen and glycogen enzymes in the liver and striated muscle of rats under altered thyroid states.

Changes induced in liver and striated muscle glycogen and glycogen enzymes (glycogen synthetase, glycogen phosphorylase and alpha-amylase) by hypothyroidism and hyperthyroidism in rats have been determined. There were no changes in liver glycogen synthetase, phosphorylase and amylase activities in the hypothyroid group. Hyperthyroid rats showed lower liver glycogen synthetase, phosphorylase a and amylase activities. In muscle, hypothyroid rats had lower phosphorylase activity. In the hyperthyroid group glycogen synthetase was increased.--The results presented do not completely agree with the glycogen levels found in both tissues studied, and they are obviously more related to other factors such as glucose availability. It can be concluded that under the conditions studied, the glycogen enzyme levels could not alone explain the variations of glycogen levels.