title: The effect of circulatory occlusion on the glycogen phosphorylase-synthetase system in human skeletal muscle.
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.
mesh_terms: D000328:Adult; D003401:Creatine / Q000378:metabolism; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism*; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000201:enzymology* / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010762:Phosphorylase a / Q000378:metabolism; D010763:Phosphorylase b / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism*; D014111:Tourniquets
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D006003:Glycogen; D010762:Phosphorylase a; D010763:Phosphorylase b; D006005:Phosphorylases; D006006:Glycogen Synthase; D003401:Creatine