The effect of circulatory occlusion on the glycogen phosphorylase‐synthetase system in human skeletal muscle.

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Abstract
The effect of circulatory occlusion upon the glycogen phosphorylase‐synthetase system in intact human muscle at rest has been investigated using the needle biopsy technique. The fraction of phosphorylase in the a form was 26% before occlusion and decreased to 9% after 40 min of occlusion. Synthetase I activity was unchanged during occlusion. After 40 min of occlusion the content of phosphocreatine was decreased by 40%, with a corresponding increase in creatine and inorganic phosphate (Pi). The observed glycogenolytic rate increased during occlusion up to 0.8 mmol glycosyl units kg‐1 dry muscle min‐1. An intracellular Pi concentration at rest of 2.0 mmol l‐1 was calculated from the activities of phosphorylase a and synthetase I assuming that under these conditions they are equal. It is concluded that the glycogenolytic rate during occlusion is a function of both the fraction of phosphorylase in the a form and the availability of Pi at the active site of the enzyme.