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Altered Glycogen Synthase and Phosphorylase Activities in Skeletal Muscle of Tetraplegic Patients
Author(s) -
Jiao Ying,
Shashkin Pavel,
Hjeltnes Nils,
WallbergHenriksson Harriet,
Katz Abram
Publication year - 2001
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/eph8602068
Subject(s) - glycogen phosphorylase , glycogen , medicine , endocrinology , skeletal muscle , glycogen synthase , enzyme , chemistry , metabolism , biology , biochemistry
Despite marked differences in both the extent of physical activity and in muscle metabolism and structure between tetraplegic and control subjects, the glycogen content in the skeletal muscle of both groups is similar. We determined whether this similarity could be explained by the activities of key enzymes of glycogen metabolism. Muscle biopsies were analysed for glycogen synthase (GS) and glycogen phosphorylase (GP) activities, as well as for metabolites. Glycogen content did not differ significantly between the two groups. Total glycogen synthase activity was reduced by almost 60% in tetraplegics ( P < 0.01), whereas total phosphorylase activity did not differ between groups. GS fractional activity did not differ between groups, whereas phosphorylase fractional activity (−/+ AMP) was significantly higher in the tetraplegics (0.08 ± 0.01, control; 0.25 ± 0.02, tetraplegics; P < 0.001). Neither uridine diphosphate (UDP)‐glucose nor glucose 6‐phosphate (G‐6‐P) content in muscle differed significantly between groups. These data demonstrate that, in tetraplegics, muscle glycogen content is preserved despite decreases in GS activity and increases in phosphorylase fractional activity. Muscle paralysis has differential effects on the activities of GS and GP.