title: Pro- and macroglycogenolysis in skeletal muscle during maximal treadmill exercise.
abstract: The purpose was to investigate the degradation of proglycogen and macroglycogen in skeletal muscle during intense exercise. Ten Standardbred trotters performed a maximal treadmill exercise test comprising a warm-up period, an exercise period, starting at 7 m/s with increments of 1 m/s every 60 s until the onset of fatigue (mean +/- s.d. 246 +/- 32 s) and a walking recovery period. Muscle biopsies were taken at rest, immediately after exercise and 15 min postexercise. The exercise caused a marked anaerobic metabolism as shown by the decrease in both muscle ATP and creatine phosphate and increase in muscle lactate. Free muscle glucose increased immediately postexercise and a further increase was noted 15 min later. There was a significant decrease (P<0.05) in proglycogen (57.1 +/- 22.2 mmol/kg dw) and macroglycogen (63.0 +/- 65.5 mmol/kg dw) during exercise. The proglycogen concentration tended to increase 15 min after exercise (19.9 +/- 27.3 mmol/kg dw; P = 0.06). The results from this study demonstrate that both proglycogen and macroglycogen contribute equally to glycogenolysis during intense exercise and suggest that glycogen resynthesis starts in the proglycogen pool.
authors.affiliation: Department of Large Animal Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala.
authors.forename: J
authors.initials: J
authors.lastname: Bröjer
authors.forename: R
authors.initials: R
authors.lastname: Jonasson
authors.forename: K
authors.initials: K
authors.lastname: Schuback
authors.forename: B
authors.initials: B
authors.lastname: Essén-Gustavsson
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001706:Biopsy / Q000662:veterinary; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006339:Heart Rate; D006736:Horses / Q000378:metabolism* / Q000502:physiology; D007773:Lactates / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*
chemical_list: D007773:Lactates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D006003:Glycogen