Mechanisms associated with hypoxia‐ and contraction‐mediated glucose transport in muscle are fibre‐dependent

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 (≈ 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.