RELEASE OF ADIPOKINETIC HORMONE DURING FLIGHT AND STARVATION IN LOCUSTA

In adult female Locusta, direct measurements of AKH (adipokinetic hormone) in the haemolymph suggest that release of hormone does not occur at a constant rate during flight. There is no direct correlation between the pattern of hormone release and the change in concentration of haemolymph total lipid during flight. The maximal amount of AKH recovered from the haemolymph was about 1.0 pmol/250 μl after 30-min flight but then decreased to about 0.4 pmol/250 μl by 90 min. In locusts starved for up to 96 hr, only traces of AKH are found in the haemolymph. Furthermore, the release of hormone during flight is severely reduced in such locusts. For example, AKH is present in the haemolymph of 24-hr starved flown locusts at only 45% of the amount in fed flown locusts and locusts starved for periods in excess of 24 hr have no detectable AKH in their haemolymph after flight. In fed locusts, experimentally produced high concentrations of haemolymph lipid bring about a reduction in the amount of AKH released into the haemolymph during a 30-min flight. The collective data from flown and starved locusts suggest that the increasing haemolymph lipid levels, which are common to both situations, exert a feedback inhibition on the release of adipokinetic hormone during flight. © 1979.