title: Mechanisms associated with hypoxia- and contraction-mediated glucose transport in muscle are fibre-dependent.
abstract: The purpose of this study was to examine the effects of hypoxia and muscle contractions on rates of 2-deoxyglucose (2-DG) transport in red and white portions of the gastrocnemius muscle of the rat. 2-DG transport was measured during the last 10 min of a 60-min hindlimb perfusion in male Wistar rats ( approximately 300 g), with or without muscle contractions of one limb. The medium was gassed with either 95% oxygen and 5% carbon dioxide or 95% nitrogen and 5% carbon dioxide to achieve normal or hypoxic conditions, respectively. Muscle contractions began after 30 min of perfusion and consisted of isometric muscle actions (200-ms trains, 100 Hz; one train per second) for two sets of 5 min, with 1-min rest between sets. 2-DG transport in white gastrocnemius was higher (P < 0.05) than basal during hypoxia (4.8-fold) and following contractions using oxygenated or hypoxic medium (4.6-fold and 5.4-fold, respectively; n=6 for each group). 2-DG transport was not different (P > 0.05) between these stimulated conditions. Similarly, 2-DG transport in red gastrocnemius was 5.1- and 4.8-fold higher (P < 0.05) than basal during hypoxia and following contractions in oxygenated medium, respectively. However, 2-DG transport following contractions during hypoxic conditions in red gastrocnemius was, unlike white gastrocnemius, higher (8.9-fold over basal; P < 0.05) than in all other conditions. These results suggest that mechanisms associated with hypoxia- and muscle contraction-mediated glucose transport are fibre type-dependent, with additive effects of the two stimuli in fast-twitch, oxidative fibres.
authors.affiliation: Department of Medical Physiology, PANUM Institute and the Copenhagen Muscle Research Centre, University of Copenhagen, Denmark.
authors.forename: J D
authors.initials: JD
authors.lastname: Fluckey
authors.forename: T
authors.initials: T
authors.lastname: Ploug
authors.forename: H
authors.initials: H
authors.lastname: Galbo
mesh_terms: D000818:Animals; D001692:Biological Transport; D005947:Glucose / Q000502:physiology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D005947:Glucose; D010100:Oxygen