Presence of an adipokinetic peptide in the corpus cardiacum of Dermaptera but not in the neurohaemal aorta, and chemical and functional identification of the peptide

Corpora cardiaca of the earwigs Labidura riparia and Forficula auricularia contain a substance that causes hyperlipaemia in migratory locusts and hypertrehalosaemia in the American cockroaches. A conspecific bioassay in L. riparia revealed that this factor is lipid-mobilizing. Isolation of the neuropeptide was achieved by single-step RP-HPLC. The primary structure of the earwig adipokinetic peptide was elucidated by automated Edman degradation in combination with matrix-assisted laser desorption/ionization mass spectrometry. It is a blocked octapeptide, pGlu-Val-Asn-Phe-Ser-Thr-Gly-Trp-NH₂, previously denoted as Grb-AKH and first identified in Gryllus bimaculatus ( Gäde & Rinehart 1987 ). The synthetic peptide co-chromatographed under various conditions with the native peptide and, in biological assays, resulted in lipid-mobilization in L. riparia when injected in low concentration.