Liver Glycogen Metabolism in Chicken. Activation Prior to Triiodothyronine-Induced Protein Synthesis Enhancement

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Abstract
The depletion in glycogen levels, before enhancement in protein synthesis, after a single Triiodothyronine (T3) injection has been previously shown in chickens and rats. The same injection of 4 μg T3 into newborn chicken increases phosphorylase a activity in liver within 4 to 10 hours, showing a maximum at 6 hours. The lag time and the maximum relate well to glycogen level depletion in chicken. However, when phosphorylase is measured in the presence of AMP, the activity is not affected by the injection of T3. Liver cAMP levels are also increased 4 h after T3 injection, but the increase is lower than for the phosphorylase a. Glucose-6-Phosphatase an enzyme of the liver carbohydrate metabolism, which is known to be activated by a single T3 injection after the protein synthesis enhancement in rats, has a lag time of 14 hours, which occurs later than the depletion in glycogen levels.