Differential distribution of pyrokinin-isoforms in cerebral and abdominal neurohemal organs of the American cockroach

Different pyrokinin isoforms were identified from major neurohemal organs o f the American cockroach. During their isolation they were recognized by bi oassay using a hyperneural muscle preparation that is sensitive to pyrokini ns, All structures were elucidated by sequence analysis and mass spectromet ry. The primary structures of the novel peptides isolated from the retrocer ebral complex are LVPFRPRL-NH2 (designated Pea-PK-3) and DHLPHDVYSPRL-NH2 ( designated Pea-PK-4). A pyrokinin, labeled Pea-PK-5, was isolated from abdo minal perisympathetic organs. Structural analysis of this peptide yielded t he sequence GGGGSGETSGMWFGPRL-NH2. The threshold concentrations of the iden tified pyrokinins for an eliciting effect on contractions of the hyperneura l muscle preparations differed dramatically. This indicates that the differ ent distribution of pyrokinin-isoform observed in neurohemal organs may be associated with different functions. This is the first report of a differen tial distribution of peptide-isoforms in the neurohemal organs of insects. (C) 1999 Elsevier Science Ltd. All rights reserved.