Carbohydrate and fat metabolism in contracting canine skeletal muscle

Summary

Isolated canine gracilis muscles were perfused in situ with a free flow (systemic blood flow; FF) or a constant flow (blood from a reservoir; CF). The nervous supply was stimulated electrically for 60 min. A-V-concentration differences for glucose, pyruvate, lactate, glycerol, FFA and O₂ were obtained as well as the concentrations of ATP, CP, glycogen and lactate in the muscle.

Resting O₂ uptake ranged from 4 to 11 μmoles×100 g⁻¹×min⁻¹ (FF; CF). A 30- and 5-fold increase in O₂ uptake occurred during stimulation in the FF and CF-experiments, respectively. The release of lactate was, however, the same (20–40 μmoles×100 g×min⁻¹) although the muscle lactate concentration was much higher in the CF experiments. In the CF experiment stimulation did not significantly increase glucose uptake which ranged from 0.3 to 3.3 μmoles×100 g⁻¹ ×min⁻¹ at rest. Conversely, stimulation resulted in a 6-fold increase in glucose uptake in the FF experiments. No definite tendency for a FFA uptake or a glycerol release was found in either experiment (FF, CF). Glycogen depletion during the stimulation period amounted to 20–30 μmoles×g⁻¹. Thus the glucose uptake could account for only 12% of the carbohydrate utilized during the stimulation period.