Quantitative studies on the release of locust adipokinetic hormone

Fractionation of methanolic extracts of haemolymph on Sephadex LH-20 made possible the measurement of the titre of adipokinetic hormone in the haemolymph of locusts. Experimentally produced high concentrations of haemolymph carbohydrate caused a delay in the mobilization of lipid during flight, and very low titres of the hormone were present in the haemolymph of locusts injected with trehalose immediately before a 25 min flight. In these locusts flight speed was higher than saline-injected controls. Although delayed lipid mobilization during flight was also seen in locusts injected with sucrose, sucrose is not utilized for flight metabolism and flight speed was not increased by the injection. Tentative estimates of the release rate (c. 1000pg/20min flight) and half life (c. 20 min) of adipokinetic hormone during flight are made. The results described suggest that during flight the rate at which trehalose disappears from the haemolymph does not play a major role in the initiation of the release of adipokinetic hormone.