Effects of trout bradykinin on the motility of the trout stomach and intestine: evidence for a receptor distinct from mammalian B 1 and B 2 subtypes

Trout bradykinin ([Arg 0 ,Trp 5 ,Leu 8 ]‐bradykinin; trout BK), recently isolated from kallikrein‐treated trout plasma, produced sustained and concentration‐dependent contractions of isolated longitudinal muscle from rainbow trout stomach (pD 2 =7.01±0.03) and proximal small intestine (pD 2 =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. The potency of trout BK on gastric smooth muscle motility was significantly (5 fold; P