GLUCOSE-UPTAKE AND TRANSPORT IN CONTRACTING, PERFUSED RAT MUSCLE WITH DIFFERENT PRECONTRACTION GLYCOGEN CONCENTRATIONS

1. Glucose uptake and transport, muscle glycogen, free glucose and glucose‐6‐phosphate concentrations were studied in perfused resting and contracting rat skeletal muscle with different pre‐contraction glycogen concentrations. Rats were pre‐conditioned by a combination of swimming exercise and diet, resulting in either low (glycogen‐depleted rats), normal (control rats) or high (supercompensated rats) muscle glycogen concentrations at the time their hindlimbs were perfused. 2. Compared with control rats, pre‐contraction muscle glycogen concentration was approximately 40% lower in glycogen‐depleted rats, whereas it was 40% higher in supercompensated rats. Muscle glycogen break‐down correlated positively (r = 0.76; P less than 0.001) with pre‐contraction muscle glycogen concentration. 3. Glucose uptake during contractions was approximately 50% higher in glycogen‐depleted hindquarters than in control hindquarters; in supercompensated hindquarters it was 30% lower. When rats with similar muscle glycogen concentrations were compared, glucose uptake in hindquarters from rats that had exercised on the preceding day was approximately 20% higher than in hindquarters from rats that had not exercised on the preceding day. 4. Muscle membrane glucose transport, as measured by the rate of accumulation of 14C‐3‐O‐methylglucose in the contracting muscles, was 25% lower in supercompensated than in glycogen‐depleted muscles at the onset as well as at the end of the 15 min contraction period. 5. Intracellular concentrations of free glucose and glucose‐6‐phosphate were higher at rest and during the entire 15‐min stimulation period in supercompensated muscles than in glycogen‐depleted muscles, and glucose uptake during contractions correlated negatively with free glucose (r = ‐0.52; P less than 0.01) as well as with glucose‐6‐phosphate (r = ‐0.49; P less than 0.01) concentrations. 6. It is concluded that: (a) The rate of glucose uptake in contracting skeletal muscle is dependent on the pre‐contraction muscle glycogen concentration. Regulating mechanisms include limitations of membrane glucose transport as well as of glucose metabolism. (b) Contractions on the preceding day have a stimulating effect on glucose uptake during contractions of the same muscles on the next day. © 1990 The Physiological Society