Effect of hypoxia on glucose metabolism in human skeletal muscle during exercise.

The effect of respiratory hypoxia on muscle glucose metabolism during short-term dynamic exercise has been investigated. Eight men cycled for 5 min at 120 +/- 6 W (mean +/- SE), which corresponded to 50% of maximal O2 uptake during normoxia (N), breathing air (N) on one occasion and 11% O2 (hypoxia-H) on the other. Biopsies were taken from the quadriceps femoris muscle before and after exercise. Oxygen uptake during exercise was not affected by H. The arterial blood glucose concentration during N exercise remained constant, but increased from 4.62 +/- 0.11 mmol l(-1) at rest to 5.22 +/- 0.19 mmol l-1 at the end of H exercise (P less than 0.05 vs N exercise). The intracellular glucose content at rest was low and did not change during N exercise, but was four times higher after exercise during H vs N (P less than 0.01). Glucose 6-P increased under both conditions but significantly more during H (P less than 0.01), while glucose 1,6-P2 was not significantly different between treatments either at rest or after exercise. It is concluded that: (1) glucose uptake by skeletal muscle during short-term exercise. It is concluded that: (1) glucose uptake by skeletal muscle during short-term exercise during H is not associated with a stoichiometric glucose utilization; (2) the inhibition of hexokinase during H (evidenced by increase in muscle glucose) is due primarily to the increase in glucose 6-P; and (3) glucose 1,6-P2 is of minor importance for the regulation of contraction-mediated flux through hexokinase in human skeletal muscle.