Regulation of substrate utilization in the flight muscle of the locust, Locusta migratoria, during flight

The concentrations of metabolites involved in carbohydrate metabolizing pathways, of amino acids and adenine nucleotides in the flight muscles of Locusta migratoria were determined during a fligt of 2 hr. During the first 15 min of flight, glycogen and glucose concentrations decreased to reach approximately constant levels. The concentration of glucose-6-phosphate increased rapidly. After an initial rise the concentration of fructose-1, 6-diphosphate, dihydroxyacetone phosphate and pyruvate reached constant levels within 1–5 min of flight. No changes were found in concentrations of other intermediates of the glycolytic pathway. The concentration of malate increased sharply, then decreased slightly, and then remained constant throughout the entire flight. Glycerol concentration increased about threefold. The concentrations of most amino acids were apparently not altered. Aspartate and alanine concentrations, however, showed a gradual increase during the first 10 min of flight, then decreased again to resting levels. The glutamate concentration decreased rapidly. The significance of this amino acid acting as a 'sparker' for citric acid cycle, is discussed along with the controlling sites of glycolytic flux.