The rate of substrate cycling between glucose and glucose 6-phosphate in muscle and fat-body of the hawk moth (Acherontia atropos) at rest and during flight

Publisher Website
Google Scholar
Abstract
The rate of substrate cycling between glucose and G-6-P was measured in tissues of the hawk moth (A. atropos). The insect was injected with [2-3H,2-14C]glucose, and after periods of time at rest or flying the animal was freeze-clamped. Separation of glucose and hexose monophosphate from the tissues was performed by paper chromatography and TLC, and the radiolabel. On the basis of the 3H/14C ratios in these compunds and the measured rate of glycolysis, the rate of cycling was calculated. The rats of cycling were 0.03, 0.10, 0.06 and 3.9 .mu.mol/min per g for fat-body at rest and during flight and for flight muscle at rest and during flight, respectively. The marked increase in the cycling rate between glucose and G-6-P upon flight contrasts with the finding of Clark, Bloxham, Holland and Lardy (1973) in the bumble-bee, in which this condition inhibited cycling. The increased rate of cycling may increase the sensitivity of glucose phosphorylation to changes in the concentrations of effectors of hexokinase should it be necessary to increase the rate of glycolysis in muscle, for example, to increase power output of the flight muscle for increased speed of flight.