The effect of epinephrine and other glycogenolytic agents on the phosphorylase A content of muscle

1. Injection of epinephrine in rats caused a marked rise in the phosphorylase a content of muscle. Nor-epinephrine had the same effect but required much larger doses. 2. Epinephrine prevented the complete disappearance of phosphorylase a in a fatigued muscle and accelerated the resynthesis of phosphorylase a during recovery from fatigue. 3. The concentration of active phosphorylase a in thin frog muscles, incubated in a solution containing epinephrine, aerobically or anaerobically rose at the expense of inactive phosphorylase b. 4. Versene inhibited the above rise. 5. The glycogenolytic agents dinitrophenol and caffeine reduced the phosphorylase a content when it was high and caused no change when it was low.