Effects of trout bradykinin on the motility of the trout stomach and intestine: Evidence for a receptor distinct from mammalian B1 and B2 subtypes

Jorgen Jensen, J. Michael Conlon

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17 Citations (Scopus)

Abstract

1 Trout bradykinin ([Arg0,Trp5,Leu8]-bradykinin; trout BK), recently isolated from kallikrein-treated trout plasma, produced sustained and concentration-dependent contractions of isolated longitudinal muscle from rainbow trout stomach (pD2 = 7.01 ± 0.03) and proximal small intestine (pD2 = 7.37 ± 0.07). The maximum responses were 85 ± 2% (stomach) and 101 ± 35% (intestine) of the corresponding responses to 10-5 M acetylcholine. Strips of circular smooth muscle from trout stomach and intestine did not contract in response to trout BK. 2 The potency of trout BK on gastric smooth muscle motility was significantly (5 fold; P ' 0.01) reduced in the presence of the cyclo-oxygenase inhibitor, indomethacin (10-5 M) and by 4 fold (P ' 0.05) in the presence of the lipoxygenase inhibitor, MK-886 (10-6 M), but there was no effect on the maximum response. Potency was also significantly reduced in the presence of 10-6 M methysergide (3 fold; P ' 0.02) and 10-6 M tetrodotoxin (2 fold, P ' 0.05) but atropine was without effect. 3 [Tyr0,Trp5,Leu8]-BK was a full agonist but was approximately 50 fold less potent (pD2 = 5.35 ± 0.08) than trout BK, [Arg0,Trp5,Leu8]des-Arg9-BK was a partial agonist (pD2 = 6.80 ± 0.03; 56 ± 7% of the maximum response to trout BK) but [Trp5,Leu8]-BK, [Trp5,Leu8]-des-Arg9-BK and mammalian BK produced no, or only very weak, contractions of the trout stomach. 4 The mammalian B1 receptor antagonist, [Leu8]des-Arg9-BK was without effect on the response of the trout stomach to trout BK. The potent mammalian B2 receptor antagonist Hoe 140 was a partial agonist (pD2 = 7.44 ± 0.12; 57 ± 15% of the maximum response to trout BK). 5 We conclude that the effects of trout BK on the motility of rainbow trout gastric smooth muscle are mediated through interaction with a receptor that has appreciably different ligand-binding properties than the mammalian B1 and B2 receptor subtypes. An involvement of arachidonic acid metabolites and 5-hydroxytryptaminergic nerves in the mechanism of action of the peptide is suggested.

Original languageEnglish
Pages (from-to)526-530
Number of pages5
JournalBritish Journal of Pharmacology
Volume121
Issue number3
DOIs
Publication statusPublished (in print/issue) - 1997

Keywords

  • B receptor
  • Bradykinin
  • Gastric motility (trout)
  • Hoe 140
  • [Leu] des-Arg-BK

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