THE EFFECT OF OCTOPAMINE ON THE GLYCOLYTIC ACTIVATOR FRUCTOSE 2,6-BISPHOSPHATE IN PERFUSED LOCUST FLIGHT-MUSCLE

A perfused locust thoracic muscle preparation was used to study the effects of octopamine on the content of fructose 2,6-bisphosphate, a potent activator of the glycolytic key enzyme phosphofructokinase, in the flight muscle of the locust Locusta migratoria. Perfusion with octopamine resulted in a significant increase in fructose 2,6-bisphosphate in flight muscle. The naturally occurring D-isomer was more potent than both D,L-octopamine and L-octopamine and gave a significant effect at 10(-7) M, a concentration observed in the haemolymph of flying locusts. The adipokinetic hormones AKH I and AKH II of Locusta had no effect on fructose 2,6-bisphosphate in perfused flight-muscle. Taurine which can be found in high concentrations in locust flight muscle was also ineffective. Electrical stimulation of perfused flight muscle (at 2 or 4Hz for 15min) caused the content of fructose 2,6-bisphosphate in flight muscle to decrease. Electrical stimulation, however, could not reverse the effect of octopamine added to the perfusion medium. It is suggested that octopamine-stimulated elevation of fructose 2,6-bisphosphate contributes to activation of glycolysis during locust flight.