The use of a cell-free perfusate in the perfused rat hindquarter: methodological concerns

The viability of using a cell-free perfusate in a rat hindlimb preparation to assess skeletal muscle glycogenesis was investigated. A perfusate containing 10 mM glucose and 10 microCi (1 Ci = 37 GBq) of D-5-3H]glucose was recycled for a 60-min period. In agreement with other studies using more complex media, oxygen uptake of the preparation indicated adequate tissue oxygenation (8 mumol.min-1.g-1). Skeletal muscle fiber type heterogeneity in basal glycogen synthesis from glucose was shown (slow oxidative greater than fast oxidative glycolytic greater than fast glycolytic fibres). Insulin (4.2 mU/mL) markedly stimulated glycogenesis from D-5-3H]glucose in the soleus (slow oxidative fiber), red gastrocnemius (fast oxidative glycolytic fiber), and white gastrocnemius muscles (p less than 0.05). A recent report indicates that tissue edema in this preparation did not affect insulin responsiveness of the tissue. In contrast, our observations indicate that glucos uptake was enhanced by insulin when edema was absent (p less than 0.05), but not when edema was present (p less than 0.05). In addition, the presence of tissue edema negated insulin-mediated glycogenesis in slow oxidative and fast oxidative glycolytic muscle (p less than 0.05 compared with control) but not in fast glycolytic muscle (p less than 0.05). These data warrant caution when using a cell-free media in the perfused rat hindquarter; however, in the absence of edema, normal responses of glucose metabolism are observed.