title: New myotropic and metabotropic actions of pyrokinins in tenebrionid beetles.
abstract: Pyrokinins are a large family of insect neuropeptides exhibiting pleiotropic activity, but are predominantly myostimulatory hormones. In this study, four pyrokinins Tenmo-PK-1 (HVVNFTPRLa), Tenmo-PK-2 (SPPFAPRLa), Tenmo-PK-3 (HLSPFSPRLa) and Zopat-PK-1 (LPHYPRLa) from the neuro-endocrine system of two tenebrionid beetles, Tenebrio molitor and Zophobas atratus, were tested in homologous bioassays to evaluate their putative myotropic and glycaemic actions. The four investigated bioassays systems (the heart, oviduct, ejaculatory duct and hindgut) revealed species-specific and organ-specific myotropic actions for the pyrokinins tested. In most bioassays with both beetles, the peptides showed myostimulatory properties with different efficacy. However, the T. molitor heart is not sensitive to Tenmo-PK-1, Tenmo-PK-2 and Tenmo-PK-3, and one of the peptides Tenmo-PK-1, is myoinhibitory on the oviduct. Tenmo-PK-2, which is also present in Z. atratus, exerted an inhibitory effect on the contractions of the heart and ejaculatory duct muscles in this beetle. Such myoinhibitory properties of pyrokinins in insects are shown here for the first time. Only one of the peptides tested, Tenmo-PK-2, stimulated a hyperglycaemic response in the haemolymph of larvae of T. molitor and Z. atratus, and this effect suggests a possible additional metabotropic function of this peptide in beetles. The differences in the myotropic and glycaemic responses to pyrokinins suggest that these peptides modulate contractions of muscles from visceral organs and free sugar levels in the haemolymph of the beetles, through complex and species-specific mechanisms.
authors.affiliation: Department of Animal Physiology and Development, Adam Mickiewicz University, Poznan, Poland. pmarcin@amu.edu.pl
authors.forename: Paweł
authors.initials: P
authors.lastname: Marciniak
authors.forename: Monika
authors.initials: M
authors.lastname: Szymczak
authors.forename: Joanna
authors.initials: J
authors.lastname: Pacholska-Bogalska
authors.forename: Neil
authors.initials: N
authors.lastname: Audsley
authors.forename: Mariola
authors.initials: M
authors.lastname: Kuczer
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Rosiński
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004353:Drug Evaluation, Preclinical; D004543:Ejaculatory Ducts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D005947:Glucose / Q000378:metabolism; D006458:Hemolymph / Q000187:drug effects / Q000378:metabolism; D007301:Insect Hormones / Q000494:pharmacology; D008297:Male; D009038:Motion; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000187:drug effects* / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects; D009479:Neuropeptides / Q000494:pharmacology*; D010057:Oviducts / Q000187:drug effects / Q000378:metabolism
chemical_list: D007301:Insect Hormones; D009479:Neuropeptides; C079229:pyrokinin; D005947:Glucose