On the Release of the Three Locust (Locusta migratoria) Adipokinetic Hormones: Effect of Crustacean Cardioactive Peptide and Inhibition by Sugars

A n existing test to m onitor the rate of adipokinetic horm one release from the corpora cardiaca (CC) of Locusta migratoria in vitro was improved, so that a constant basal ra te of release was achieved and the am ount of released Lom -AKH-I, II and III could be quantified by HPLC. This test system was subsequently used to dem onstrate that a small peptide, which has been found in a few insect species including L. migratoria, crustacean cardioactive p ep ­ tide (C C A P), induces release of all three AKHs. M oreover, 80 mM trehalose reduces C CA Pinduced release of A K H s in vitro, and 160 mM glucose reduces this release even further. G lucose also had a greater inhibitory effect than trehalose on the spontaneous release and inhibited the high potassium -stim ulated release of A KH from the CC in vitro. Eighty mM sucrose, on the o ther hand, had no effect on the release of AKH. The effect of trehalose and glucose could be due to their use as an energy source, with trehalose first having to be converted to glucose. W hatever the stimulus, the three AKH s are released in the sam e p ro ­ portions as they are found in the CC, which in vivo would make Lom -A K H-I, the most abundant A K H , the m ajor effector of the biological effects of A K H s in adult locusts.