title: Cardiovascular actions of lungfish bradykinin in the unanaesthetised African lungfish, Protopterus annectens.
abstract: Bradykinin (BK) isolated from plasma of the African lungfish, Protopterus annectens, contains four amino acid substitutions compared with BK from mammals (Arg(1)-->Tyr, Pro(2)-->Gly, Pro(7)-->Ala, Phe(8)-->Pro). Bolus intra-arterial injections of synthetic lungfish BK (1-1000 pmol/kg body wt.) into unanaesthetised, juvenile lungfish (n=5) produced a dose-dependent increase in arterial blood pressure and pulse pressure. The maximum pressor response occurred 2-3 min after injection and persisted for up to 15 min. The threshold dose producing a significant (P<0.01) rise in pressure was 50 pmol/kg and the maximum increase, following injection of 300 pmol/kg, was 9.3 +/- 2.3 mmHg. Injection of the higher doses of lungfish BK produced a significant (P<0.05) increase in heart rate (2.8 +/- 0.8 beats/min at 100 pmol/kg). In contrast, bolus intra-arterial injections of mammalian BK, in doses up to 1000 pmol/kg, produced no significant cardiovascular effects in the lungfish. The data support the existence of a functioning kallikrein-kinin system in the lungfish and demonstrate that the ligand-binding properties of the receptor(s) mediating the cardiovascular actions of lungfish BK are appreciably different from mammalian B1 and B2 receptors.
authors.affiliation: School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Balment
authors.forename: Maria A
authors.initials: MA
authors.lastname: Masini
authors.forename: Mauro
authors.initials: M
authors.lastname: Vallarino
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
mesh_terms: D000349:Africa; D000758:Anesthesia; D000818:Animals; D001011:Aorta / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000138:chemical synthesis / Q000494:pharmacology*; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D005260:Female; D005399:Fishes / Q000502:physiology* / Q000601:surgery; D006339:Heart Rate / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001920:Bradykinin