Cardiovascular actions of lungfish bradykinin in the unanaesthetised African lungfish, Protopterus annectens

Richard J. Balment, Maria A. Masini, Mauro Vallarino, J. Michael Conlon

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7 Citations (Scopus)


Bradykinin (BK) isolated from plasma of the African lungfish, Protopterus annectens, contains four amino acid substitutions compared with BK from mammals (Arg1 → Tyr, Pro2 → Gly, Pro7 → Ala, Phe8 → 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.

Original languageEnglish
Pages (from-to)467-474
Number of pages8
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Issue number2
Publication statusPublished (in print/issue) - 2002


  • African lungfish
  • Arterial blood pressure
  • Bradykinin
  • Cardiovascular
  • Dipnoi
  • Heart rate


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