Specific binding and proteolytic inactivation of bradykinin by membrane vesicles from pig intestinal smooth muscle

Cyclic and linear bradykinin analogues: implications for B2 antagonist design

Bradykinin (BK, Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) antagonists are potentially useful for treating inflammation, pain and severe trauma. To identify what chemical features might promote effective antagonism, we replaced Arg1 and Pro7 with structurally constrained and proteolytic-resistant residues, such as Bip (biphenylalanine), Dip (diphenylalanine) or 2Ind (indane amino acid). To determine which BK folding might lead to favourable interactions with receptors, the effects of cyclo(3,8) vs. cyclo(5,8) analogues were compared. The resulting BK analogues were examined for their agonistic and antagonistic activities in guinea pig ileum, rat uterus and depressor assays. The results suggest that co-planarity of the residue-7 side chain with its backbone NH is important for potent agonism as well as antagonism, and a D-directed side chain is crucial for antagonism. For residue-1 an L-orientation is important, and Dip1 may mimic a folded Arg1 side chain to elicit agonistic activities, with Bip1 mimicking an extended Arg1 side chain to elicit inhibitory activities. However, ileal and uterine receptors appear to prefer differently folded BK. For ileum, a BK conformation in which residues-3 and -8 are proximal to each other, but apart from residue-5, led to improved pA2.

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

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.

Role of peptidases in bradykinin-induced increase in vascular permeability in vivo

The purpose of this study was to examine whether neutral endopeptidase and angiotensin I-converting enzyme, two membrane-bound metalloenzymes that are widely distributed in the microcirculation, play a role in bradykinin-induced increase in vascular permeability in the hamster cheek pouch. Changes in vascular permeability were quantified by counting the number of leaky sites and by calculating the clearance of fluorescein isothiocyanate (FITC)-dextran (molecular mass, 70,000 d) during suffusion of the cheek pouch with bradykinin. Bradykinin produced a concentration- and time-dependent increase in the number of leaky sites and clearance of FITC-dextran. The selective, active site-directed neutral endopeptidase inhibitors phosphoramidon (1.0 microM) and thiorphan (10.0 microM) and the selective angiotensin I-converting enzyme inhibitor captopril (10.0 microM) each shifted the concentration-response curve to bradykinin significantly to the left. During suffusion with bradykinin (1.0 microM) and phosphoramidon, the number of leaky sites increased significantly from 17 +/- 2 to 27 +/- 4 sites per 0.11 cm2 (mean +/- SEM, p less than 0.05), and FITC-dextran clearance increased significantly from 1.0 +/- 0.2 to 2.1 +/- 0.3 ml/sex x 10(-6).(ABSTRACT TRUNCATED AT 250 WORDS)

Antagonistic effect of Mandevilla velutina extract on kinin-induced contractions of guinea-pig and cat ileum longitudinal smooth muscle

1. The effect of aqueous/alcoholic extract of Mandevilla velutina on bradykinin (BK), lysyl-bradykinin (L-BK), methionyl-lysyl-bradykinin (M-L-BK), acetylcholine (Ach) and histamine (Hist)-induced contractions in the isolated muscle from guinea-pig and cat ileum was analysed. 2. In the presence of atropine and pyrilamine, the extract (0.5-2 mg/ml) caused a parallel and concentration-dependent rightward displacement to all three kinins dose-response curves. Schild plots yielded nominal PA2 values (g/ml) of 3.2, 3.3 and 3.8 respectively, but the slopes of BK and M-L-BK were different from unity. 3. M. velutina extract (1 and 2 mg/ml) also concentration-dependently inhibited the contractile response evoked by BK in the isolated cat ileum and produced only slight depressions of the Ach and His-contractions (less than 20%) suggesting some selectivity towards kinin receptors. 4. These findings and those previously reported indicate that the active principles present in the crude extract of M. velutina competitively antagonizes kinin-induced contractions in several smooth muscle preparations.