Muscle action and glycogen phosphorylysis

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Abstract
Brei and extract of denervated muscle have subnormal phosphorylytic activities towards glycogen. The phosphorylytic activity begins to fall off about 10 days after denervation. Other forms of severe atrophy, such as that induced by tendotomy or application of plaster cast, do not entail any loss of phosphorylytic activity towards glycogen. In the 3d wk. after denervation some decrease is also manifest in glyco-lytic ability. Electrical stimulation of muscle failed to affect the phosphorylytic ability. Strychnine convulsions were likewise without effect. Embryo muscle and muscle of the newly born animal manifest only minimal phosphorylytic activity. As the muscles come into full function, the phosphorylytic activity increases and gradually approaches the normal. The phosphorylytic activity of different muscle types decreases as follows white muscle > red muscle > heart > smooth muscle. Except for denervated and smooth muscle the phosphorylase content of different muscle types is fairly uniform. Denervated muscle shows half the phosphorylase activity of normal muscle. Lowered phosphorylytic activity was found, however, always to entail a marked diminution of the phosphogluco-mutase conc. In muscle, the primary limiting factor of phosphorylytic glycogen breakdown and glycogen synthesis is the glucomutase. The significance of phosphorylytic glycogen breakdown for muscle function has been discussed.

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