On the release of the three locust (Locusta migratoria) adipokinetic hormones: Effect of crustacean cardioactive peptide and inhibition by sugars

An existing test to monitor the rate of adipokinetic hormone release from t he corpora cardiaca (CC) of Locusta migratoria in vitro was improved, so th at a constant basal rate of release was achieved and the amount of released Lom-AKH I, II and III could be quantified by HPLC. This test system was su bsequently used to demonstrate that a small peptide, which has been found i n a few insect species including L. migratoria, crustacean cardioactive pep tide (CCAP), induces release of all three AKHs. Moreover, 80 mM trehalose r educes CCAP-induced release of AKHs in vitro, and 160 mM glucose reduces th is release even further. Glucose also had a greater inhibitory effect than trehalose on the spontaneous release and inhibited the high potassium-stimu lated release of AKH from the CC in vitro. Eighty mM sucrose, on the other hand, had no effect on the release of AKW. The effect of trehalose and gluc ose could be due to their use as an energy source, with trehalose first hav ing to be converted to glucose. Whatever the stimulus, the three AKHs are r eleased in the same proportions as they are found in the CC, which in vivo would make Lom-AKPI-I, the most abundant AKH, the major effector of the bio logical effects of AKHs in adult locusts.