Several isoforms of locustatachykinins may be involved in cyclic AMP mediated release of adipokinetic hormones from the locust corpora cardiaca

Four locustatachykinins (LomTK I-IV) were identified in about equal amounts in extracts of corpora cardiaca of locusts, using reverse-phase high-performance liquid chromatography and radioimmunoassay with synthetic LomTK I-IV as standards. Brain extracts also contained the four isoforms in roughly equimolar concentrations. Retrograde tracing of the nervi corporis cardiaci II (NCC II) in vitro with Lucifer yellow in combination with LomTK immunocytochemistry revealed that about half of the secretomotor neurons in the lateral part of the protocerebrum projecting into the glandular lobe of the corpora cardiaca (CCG) contain LomTK-immunoreactive material. Since the four LomTKs are present in the CCG, these four or five neurons in each hemisphere are likely to contain colocalized LomTK I-IV. The role of two of the LomTKs in the regulation of the release of adipokinetic hormones (AKHs) from the adipokinetic cells in the CCG in the locust was investigated. Experiments performed in vitro showed that LomTK I and II induced release of AKH in a dose-dependent manner. These peptides also rapidly and transiently elevated the cyclic AMP-content of the CCG. The peak level of cyclic AMP occurred about 45 seconds after stimulation with LomTK. These results support the proposal that LomTKs are involved in controlling the release of the adipokinetic hormones and suggest that all LomTK isoforms may participate in this cyclic AMP-mediated event. (C) 1999 Academic Press.status: publishe

Isolation and characterization of an adipokinetic hormone release-inducing factor in locusts: The crustacean cardioactive peptide

A methanolic extract of 700 desert locust (Schistocerca gregaria) brains contains several factors that stimulate the in vitro release of adipokinetic hormone (AKH) by glandular cells of locust (Locusta migratoria and Schistocerca gregaria) corpora cardiaca. The most potent one has now been fully identified. Matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis revealed a mass of 954.6 Da. The primary structure of the peptide, Pro-Phe-Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2, appeared identical to that of a previously identified crustacean cardioactive peptide. This myotropin was first isolated from the shore crab, Carcinus maenas, and later from several insect species, but was never reported in the context of AKH release.status: publishe

Isolation and characterization of an adipokinetic hormone release-inducing factor in locusts : the crustacean cardioactive peptide

A methanolic extract of 700 desert locust (Schistocerca gregaria) brains contains several factors that stimulate the in vitro release of adipokinetic hormone (AKH) by glandular cells of locust (Locusta migratoria and Schistocerca gregaria) corpora cardiaca. The most potent one has now been fully identified. Matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis revealed a mass of 954.6 Da. The primary structure of the peptide, Pro-Phe-Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2, appeared identical to that of a previously identified crustacean cardioactive peptide. This myotropin was first isolated from the shore crab, Carcinus maenas, and later from several insect species, but was never reported in the context of AKH release. The present study shows that synthetic crustacean cardioactive peptide induces the release of AKH from corpora cardiaca in a dose-dependent manner when tested in concentrations ranging from 10(-5)-10(-9) M. This is the first demonstration in invertebrates of a peptide neurohormone controlling the release of a second peptide hormone