Does insulin release kinins in rats?

Rat uterus maintained in situ was used as a bioassay of kinins possibly released in vivo by hyperglycaemia or insulin. Intravenous injections of bradykinin induced contractions of rat uterus which were suppressed by HOE 140, a bradykinin B2 receptor antagonist. Des-Arg9-bradykinin, a kinin B1 receptor agonist, did not elicit any response. After propranolol, the effects of bradykinin were enhanced and dose-dependent. This potentiation did not appear in adrenalectomized rats. Captopril, an angiotensin-converting enzyme (ACE) inhibitor, largely increased the effects of bradykinin. In animals pretreated with propranolol, captopril and atosiban, an oxytocin antagonist, intravenous infusion of glucose induced hyperglycaemia and after a delay increased the uterine contractile activity. This contractile effect of glucose was abolished by HOE 140. Infusion of insulin with glucose induced contractions of the uterus. These responses did not appear or were suppressed by HOE 140 or by soya bean trypsin inhibitor (SBTI), a plasma kallikrein inhibitor. These results are direct evidence that insulin induces a release of kinins.     

Role of the bradykinin B2 receptor for the local and systemic inflammatory response that follows severe reperfusion injury

1. Bradykinin (BK) appears to play an important role in the development and maintenance of inflammation. Here, we assessed the role of the BK B(2) receptor for the injuries that occur after ischemia and reperfusion (I/R) of the territory irrigated by the superior mesenteric artery. 2. Tissue (lung and duodenum) kallikrein activity increased after ischemia with greater enhancement after reperfusion. A selective inhibitor of tissue kallikrein, Phenylacetyl-Phe-Ser-Arg-N-(2,3-dinitrophenyl)-ethylenediamine (TKI, 0.001-10 mg ml(-1)), inhibited kallikrein activity in a concentration-dependent manner in vitro. In vivo, pretreatment with TKI (30 mg kg(-1)) prevented the extravasation of plasma and the recruitment of neutrophils. 3. Similarly, the bradykinin B(2) receptor antagonists, HOE 140 (0.01-1.0 mg kg(-1)) or FR173657 (10.0 mg kg(-1)), inhibited reperfusion-induced increases in vascular permeability and the recruitment of neutrophils in the intestine and lungs. 4. In a model of more severe I/R injury, HOE 140 (1.0 mg kg(-1)) inhibited the increase in vascular permeability, neutrophil recruitment, haemorrhage and tissue pathology. Furthermore, HOE 140 significantly inhibited the elevations of TNF-alpha in tissue and serum and partially prevented lethality. This was associated with an increase in the concentrations of IL-10 in tissue and serum. 5. Thus, our results demonstrate that, following intestinal I/R injury, there is an increase in tissue kallikrein activity and activation of BK B(2) receptors. B(2) receptor activation is essential for the development of inflammatory tissue injury and lethality. These results contrast with those of others showing that BK mostly exerts a protective role during I/R injury.     

The inflammatory reaction induced by formalin in the rat paw

The involvement of bradykinin and some other inflammatory mediators in formalin-induced oedema and plasma extravasation was examined. Formalin was injected in rat paws at two doses, 1.75% or 5%. The lower dose induced the development of an immediate oedema associated with a progressive accumulation of ¹²⁵I-labelled albumin in the paws. These changes were suppressed by pretreatment with capsaicin or xylocaine. They were abolished by RP67580, a NK₁ receptor antagonist, and increased by phosphoramidon or diprotin A. They were not affected by HOE140, a bradykinin B₂ antagonist, captopril, methysergide, mepyramine, indomethacin, ketoprofen or l-N ^G-nitroarginine. The higher dose of formalin induced a swelling of the paws which took place in two phases associated with two periods of increase in vascular permeability. This oedema was reduced by pretreatment with capsaicin but not with xylocaine. It was reduced by RP67580 injected before or 30 min after formalin. It was inhibited by mepyramine, methysergide, indomethacin and NS-398, a cyclooxy-genase-2 inhibitor. It was not modified by HOE140. Its development was similar in normal and kininogen-deficient rats. We concluded that formalin administered at a low dose induces an oedema which mainly results from a neurogenic inflammation mediated by neuropeptides such as substance P. At higher doses, formalin induces an oedema which mainly depends on the release of substance P, prostanoids, 5-hydroxytryptamine and histamine. Bradykinin plays no significant role in the vascular changes whereas this peptide has been reported to participate in the stimulation of nociceptive afferent neurons. This discrepancy could be explained by a difference in the threshold of stimulation of the nociceptive neurons and that of the cells of the vascular walls, or by a formation of kinins in close contact of the neurons. Received: 29 June 1998 / Accepted: 20 November 1998     

Effects of the bradykinin antagonist, HOE 140, in experimental acute pancreatitis.

1. The novel bradykinin antagonist, HOE 140, completely blocked the fall in rabbit blood pressure caused, not only by i.v. bradykinin, but also by i.v. kallikrein. This shows that both the effects of exogenously administered bradykinin and those of endogenously released kinins are antagonized by HOE 140. 2. Acute pancreatitis was induced in rats by i.v. infusion of the cholecystokinin analogue, caerulein. This treatment resulted in massive oedema of the pancreas, increased activities of amylase and lipase in serum and a characteristic, biphasic fall in blood pressure. 3. HOE 140 prevented the caerulein-induced pancreatic oedema and the second phase of hypotension whereas NPC 349, a widely used, but short-acting, bradykinin antagonist did not show a significant inhibition. HOE 140, in contrast to its inhibitory effects on caerulein-induced pancreatic oedema and hypotension, significantly augmented the increases in amylase and lipase activities in serum. 4. It is concluded that in this model of acute pancreatitis, the release of kinins induces pancreatic oedema and hypotension. Prevention by HOE 140 of the kinin-induced oedema allows the pancreatic enzymes to leave the tissue without hindrance and thus will diminish subsequent pathological events. It is suggested that the results obtained with the highly potent and long-acting bradykinin antagonist, HOE 140, provide a pharmacological basis for a clinical trial in acute pancreatitis.     

Action of bradykinin potentiating factor (BPF) and dimercaprol (BAL) on the responses to bradykinin of isolated preparations of rat intestines

BPF and BAL inhibited kininase activity of homogenates of rat intestine. However, BFP potentiated and BAL inhibited the contractions induced by bradykinin on rat isolated duodenum (low calcium solution) and terminal ileum (normal calcium solution). Neither BPF nor BAL affects the relaxation induced by bradykinin of rat duodenum bathed in normal Tyrode. These results suggest that two different types of pharmacological receptor are involved in the action of bradykinin on rat intestine, and that other factors besides the inhibition of agonist destruction participate in the mechanism of potentiation of kinin action by BPF.     

Release of [hydroxyproline3]-kinins by tissue kallikreins of pig, rat and man

To determine the susceptibility of kininogens containing the recently described [Hyp3]-bradykinin moiety to cleavage by tissue kallikreins, we have studied the release of [Hyp3]-kinins from heat inactivated human plasma by purified tissue kallikreins. Kallikreins from man and pig were employed and compared with purified rat urinary kallikrein which is known to have a different cleavage specificity. Kinins released were separated by a modified reversed phase HPLC method and quantitated by bioassay and radioimmunoassay. Human urinary kallikrein and hog tissue kallikreins released 85-90% of the total kinins as Lys-bradykinin and 10-15% as [Hyp3]-Lys-bradykinin. In contrast, rat urinary kallikrein released 77% as bradykinin, 22% as [Hyp3]-bradykinin and negligible amounts of [Hyp3]-Lys-bradykinin from the identical substrate source indicating that rat tissue kallikreins prefer the Lys-Arg-bond within both unhydroxylated and hydroxylated kininogens. Therefore, hydroxylation of human kininogens apparently does not affect their ability to serve as substrates for tissue kallikreins with different cleavage specificities.     

Characterization of bradykinin receptors mediating catecholamine release in PC12 cells

The rat pheochromocytoma cell line PC12, which is a widely used model for analyzing stimulus-secretion coupling, was investigated for the effects of kinins on catecholamine release. Subtypes of kinin receptors were characterized using the B₁ agonist desArg⁹-bradykinin, the B₂ agonist bradykinin and the B₂ antagonists [Thi^5,8, D-Phe⁷]-bradykinin, D-Arg[Hyp³, D-Tic⁷, Oic⁸]-bradykinin (HOE 890307) and D-Arg-[Hyp³, Thi⁵, D-Tic⁷, Oic⁸]-bradykinin (HOE 140). The effectiveness of acute and chronic exposure to angiotensin I converting enzyme inhibitors as well as pretreatment of the cells with bacterial lipopolysaccharides in modulating B₁ or B₂ receptor systems was also tested.Bradykinin stimulated noradrenaline release from PC12 cells at low concentrations (EC₅₀ = 1 nM), maximally inducing a release of 43.7% of the cellular content within 15 min. In comparison with acetylcholine and K⁺-induced depolarization, bradykinin was the most effective stimulus. DesArg⁹-bradykinin was only effective at very high concentrations (> 30 M). Like in other neuronal cells, the B₂-specific partial antagonist [Thi^5,8, D-Phe⁷]-bradykinin acted as a low-affinity agonist without any antagonistic effects. The B₂ antagonists HOE 890307 and HOE 140 exerted no agonistic effects and concentration-dependently inhibited bradykinin-induced noradrenaline release, showing competitive antagonism with K_i values of 1.38 nM and 0.66 nM, respectively. Only at the highest concentration used (1 M), HOE 140 did depress the maximal response to bradykinin. HOE 890307 also abolished the effects of desArg⁹-bradykinin and [Thi^5,8, D-Phe⁷]-bradykinin. Acute or chronic inhibition of the angiotensin I converting enzyme or application of lipopolysaccharides, which all can lead to induction of the B₁ receptor subtype in vivo, did not alter the secretory response of PC12 cells to either bradykinin (0.1 and 30 nM) or desArg⁹-bradykinin (1 M).In conclusion, noradrenaline release from PC12 cells is stimulated via B₂, but not B₁, receptors. Despite the fact that the receptor system is highly susceptible to stimulation by low-affinity ligands, HOE 890307 and HOE 140 are pure antagonists, with only high concentrations of HOE 140 (> 1 M) showing a non-competitive type of inhibition. Induction of B₁ receptors which could stimulate noradrenaline release could not be demonstrated in this model. The possible role of bradykinin in modulating sympathetic neurotransmission during inhibition of angiotensin I converting enzyme is discussed.     

Roles of kallikrein-kinin system in acute inflammation: studies on high- and low-molecular weight kininogens-deficient rats (B/N-Katholiek strain)

Carrageenin-induced paw edema in HMW- and LMW-kininogens-deficient rats was significantly less than that in normal rats. There are three kininogens, HMW-, LMW- and T-kininogens, in normal rat plasma, but B/N-Katholiek rat plasma contains only T-kininogen. The pretreatment with captopril, a kiniase II inhibitor, enhanced paw swelling of normal rats, but not that of the deficient rats, indicating that bradykinin released from HMW-kininogen may have a role for the swelling but T-kinin may not be released in this inflammation.     

Human bradykinin B(2) receptor is activated by kallikrein and other serine proteases

Bradykinin (BK) and kallidin (Lys-BK), liberated from kininogens by kallikreins, are ligands of the BK B(2) receptor. We investigated whether kallikreins, besides releasing peptide agonist, could also activate the receptor directly. We studied the effect of porcine and human recombinant tissue kallikrein and plasma kallikrein on [Ca(2+)](i) mobilization and [(3)H]arachidonic acid release from cultured cells stably transfected to express human BK B(2) receptor (CHO/B(2), MDCK/B(2), HEK/B(2)), and endothelial cells were used as control cells. As with BK, the actions of kallikrein were blocked by the B(2) antagonist, HOE 140. Kallikrein was inactive on cells lacking B(2) receptor. Kallikrein and BK desensitized the receptor homologously but there was no cross-desensitization. Furthermore, 50 nM human cathepsin G and 50 nM trypsin also activated the receptor; this also was blocked by HOE 140. Experiments excluded a putative kinin release by proteases. [(3)H]AA release by BK was reduced by 40% by added kininase I (carboxypeptidase M); however, receptor activation by tissue kallikrein, trypsin, or cathepsin G was not affected. Prokallikrein and inhibited kallikrein were inactive, suggesting cleavage of a peptide bond in the receptor. Kallikreins were active on mutated B(2) receptor missing the 19 N-terminal amino acids, suggesting a type of activation different from that of thrombin receptor. Paradoxically, tissue kallikreins decreased the [(3)H]BK binding to the receptor with a low K(D) (3 nM) and inhibited it 78%. Thus, kallikreins and some other proteases activate human BK B(2) receptor directly, independent of BK release. The BK B(2) receptor may belong to a new group of serine protease-activated receptors.     

Comparative study of endotoxin-induced hypotension in kininogen-deficient rats with that in normal rats.

1. The aim of this study was to clarify the role of endogenous bradykinin (BK) in the hypotensive response induced by lipopolysaccharide (LPS) by comparing the degree of hypotension caused by LPS in a strain of specific pathogen-free (SPF) Brown Norway (B/N), kininogen-deficient mutant Katholiek rats with that of B/N normal Kitasato rats. 2. The dose-dependent hypotensive responses caused by intravenous injection of BK (1-100 nmol kg-1) or platelet-activating factor (PAF, 0.003-1 microgram kg-1), were not different in the two strains of rats used. However, there was a strong difference in the hypotensive response induced by LPS in kininogen-deficient and normal rats; in normal rats the hypotensive response was composed of two phases (15 min and 70-80 min after LPS injection), but in kininogen-deficient rats LPS caused a delayed (second phase), but not an acute (first phase) hypotension. 3. We demonstrate that Hoe 140 (1 mg kg-1, i.v.) is a potent, selective, and long-lasting antagonist of the hypotensive effects of BK. Hoe 140 diminished the hypotension caused by LPS in normal rats to the level observed in kininogen-deficient rats, but had no effect on the hypotension caused by LPS in kininogen-deficient rats. 4. TCV309 (0.1 mg kg-1, i.v.) selectively inhibited the hypotension caused by repetitive injection of PAF for up to 180 min. Pretreatment with TCV309 caused a near complete inhibition of the LPS-induced hypotension in kininogen-deficient and normal B/N rats. 5. In the normal rats, dexamethasone (0.5 mg kg-1, i.p.) inhibited the second phase of the hypotension induced by LPS, but not the first phase of the hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bradykinin receptor antagonists and cyclooxygenase inhibitors in vincristine-and streptozotocin-induced hyperalgesia

Pain that accompanies neuropathy is difficult to treat. Analgesics administered as monotherapies possess low activities in relieving this kind of pain.The effect of the simultaneous administration of indomethacin (a preferential inhibitor of cyclooxygenase-1; COX-1) or celecoxib (a relatively selective inhibitor of cyclooxygenase-2; COX-2), with selective antagonists of bradykinin₂ (B₂) bradykinin1 (B₁) receptors (HOE 140 or des-Arg¹⁰-HOE 140) on the eleviation of diabetic and toxic neuropathic pain was investigated.Pretreatment with indomethacin (0.1 mg/kg, sc) increased the antihyperalgesic activity of low daily doses of HOE 140 or des-Arg¹⁰HOE 140 (70 nmol/kg, ip) in a diabetic (streptozotocin(STZ)-induced) neuropathy/hyperalgesia experimental model. Premedication with celecoxib before HOE 140 or des-Arg¹⁰HOE 140 administration resulted in a gradual reduction of STZ hyperalgesia. Furthermore, on days 23–24, almost complete abolishment of STZ hyperalgesia was observed. After cessation of drug administration, hyperalgesia quickly returned to the baseline threshold.The results of this study suggest that inhibitors of cyclooxygenases can increase the antihyperalgesic activity of selective antagonists of B₂ and B₁ receptors in diabetic and toxic neuropathic pain models. These observations may be clinically relevant.     

Soluble dextran complexes of kallikrein. Bradykinin and enzyme inhibitors.

Pig pancreatic kallikrein, the protease inhibitor aprotinin (Trasylol), SQ 21541 (Arg-Pro-Gln-Ile-Pro-Pro, an angiotensin I converting enzyme or kininase II inhibitor), and bradykinin were each coupled covalently to soluble dextran with an average molecular weight of 500,000. Dextran had been activated either with cyanogen bromide (CNBr) or sodium meta-periodate (SMP). Of the reactants, 56 per cent of kallikrein, 35 per cent of aprotinin and 23 per cent of bradykinin had been bound to CNBr-activated dextran, while 38 per cent of SQ 21541 and 45 per cent of bradykinin had been bound to SMP-activated dextran. The activities of the complexes were determined in vitro. Kallikrein CNBr-dextran had 72 per cent of the esterase activity of non-coupled kallikrein. Aprotinin CNBr-dextran had 41 per cent of the kallikrein inhibitory activity of free aprotinin, and SQ 21542 SMP-dextran had 24 per cent of the converting enzyme inhibitory activity of the free peptide in vitro. The relative potencies of bradykinin CNBr-dextran and bradykinin SMP-dextran on the isolated rat uterus were 6 and 29 per cent those of native bradykinin. Their relative immunological potencies, however, were 92 and 80 per cent as determined by radioimmunoassay. Free and bound bradykinin inhibited the hydrolysis of hippuryl-glycylglycine by converting enzyme, but the coupled peptide inhibited less than the free kinin. Bradykinin coupled covalently to dextran was inactivated more slowly by converting enzyme than free bradykinin.     

Airway hyperresponsiveness to bradykinin induced by allergen challenge in actively sensitised Brown Norway rats

The mechanism(s) of bradykinin-induced bronchoconstriction was investigated in the Brown Norway (BN) rat model of allergic asthma. Bronchoconstrictor responses to i.v. bradykinin in BN rats were maximally augmented 24 h following challenge with allergen and declined at later time points. Histological evaluation of the inflammatory status of the lungs after ovalbumin (OA) challenge showed a marked inflammatory response, which was maximal at 24 h and declined thereafter. However, pretreatment with budesonide did not inhibit the augmented bronchoconstrictor response to bradykinin 24 h after allergen challenge. The selective B₁ receptor agonist, Lys-[desArg⁹]-BK had no bronchoconstrictor effects, whereas the selective B₂ receptor antagonist, HOE 140, abolished the response to bradykinin in OA-challenged animals. The augmented response to bradykinin was not affected by methysergide, indomethacin, disodium cromoglycate, iralukast, the 5-lipoxygenase inhibitor, CGS8515, or the NK₂ receptor antagonist, SR48968. It was, however, partially inhibited by atropine both in saline- and OA-challenged animals. Pretreatment with captopril and thiorphan markedly potentiated responses to bradykinin both in saline- and OA-challenged animals.Thus, augmentation of the bronchoconstrictor response to bradykinin occurs in actively sensitised BN rats 24 h after challenge with OA and is associated with marked pulmonary inflammation. The response is entirely B₂ receptor mediated and approximately 50% of the response is cholinergic. However, mast cell activation, the products of the cyclooxygenase or 5-lipoxygenase pathways and tachykinins are not involved. Peptidase inhibition mimics the effect of allergen challenge on the bronchoconstrictor response to bradykinin and it remains possible that the mechanism of the augmented response to bradykinin following allergen challenge involves downregulation of peptidase activity as a consequence of the inflammatory response.     

KALLIKREINS AND KININS IN INFLAMMATORY-LIKE EVENTS IN THE REPRODUCTIVE TRACT

The normal reproductive events of proliferation of the endometrial lining of the uterus during the menstrual cycle and ovulation have been likened to inflammatory-like events. The kallikrein-kinin system is involved in inflammatory processes in many tissues. In this review, we identify which components of the kallikrein-kinin system — the enzyme, tissue kallikrein; the substrate, low molecular weight kininogen and the effector receptor for the generated bradykinin peptide, the B2 receptor — have been identified in the uterus and ovary and their known involvement in the function of these organs. All three components have been localized to the glandular epithelial cells of the human endometrium. Tissue kallikrein gene expression is elevated midcycle when estrogens levels are also rising. This is also a time of extensive endometrial proliferation and tissue remodelling in preparation for embryo implantation, an event which is likened to other inflammatory processes. Similarly, tissue kallikrein gene expression was elevated following the estrogen surge at proestrous in the rat uterus, suggesting tissue kallikrein gene expression may be regulated by estrogens. Tissue kallikrein enzyme activity and gene expression has been demonstrated in the rat ovary and shown to be variously altered at the time of ovulation. Bradykinin has also been implicated in the expulsion of the ovum at the time of ovulation. These findings show that various components of the kallikrein-kinin system are present in the uterus and ovary. Further studies are required to more fully delineate their role in reproductive function.     

HOE 140, a new highly potent and long-acting bradykinin antagonist in conscious rats.

The inhibitory effects of the new bradykinin antagonist HOE 140 (D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg) on depressor responses to exogenous bradykinin were investigated in conscious rats and compared with those of the bradykinin antagonist B4146 (D-Arg-Hyp-Pro-Gly-Thi-Ser-D-Pro-Thi-Arg). HOE 140 showed a 250-700-fold higher potency in vivo and a much longer biological half-life than B4146. Plasma catecholamines were not increased after application of HOE 140, indicating that this compound did not interfere with catecholamine release. HOE 140 proved to be a highly potent, specific and long-acting bradykinin B2-receptor antagonist.     

Farnesoid X receptor regulates vasoreactivity via Angiotensin II type 2 receptor and the kallikrein‐kinin system in vascular endothelial cells

Vascular farnesoid X receptor (FXR) ligands have been shown previously to regulate vascular tension. This study investigated whether FXR activation regulates vasoreactivity via the angiotensin II (Ang II) type 2 receptor (AT₂R) and the kallikrein‐kinin system in rat aortic vascular endothelial cells (RAECs). Protein abundances of Ang II type 1 receptor (AT₁R), AT₂R, bradykinin type 1/2 receptor (B₁R, B₂R), small heterodimer partner‐1 (SHP‐1) and the endothelial and inducible NO synthases (eNOS/iNOS) were analysed by Western blotting. Real‐time quantitative polymerase chain reaction was performed to analyse expression of eNOS and iNOS mRNA. Kallikrein activity and bradykinin content were assayed using spectrophotometry and a bradykinin assay kit, respectively. Aortic vasoconstriction and vasodilation were also investigated following FXR activation in the presence or absence of AT₂R and B₂R blockade. It was found that the FXR agonists GW4064 and INT‐747, in a dose‐dependent manner, increased the protein abundance of AT₂R, B₂R and SHP‐1 and decreased that of AT₁R. AT₂R blockade with PD123319 reversed effects of FXR agonists on kallikrein activity and levels of SHP‐1, B₂R and bradykinin. Moreover, it was found that GW4064 and INT‐747 upregulated expression of eNOS and enhanced NOS activity, which attenuated vasoconstriction and induced vasodilation, respectively. These effects were partially reversed by PD123319 and by B₂R blockade with HOE140. The current work suggests that FXR regulates vascular tension by controlling the eNOS‐NO system via activation of a pathway mediated by AT₂R‐B₂R pathway in RAECs.     

Inhibition of oxytocic and hypotensive activities of bradykinin by bradykinin-binding antibodies

The influence of bradykinin-binding antibodies on the hypotensive and the oxytocic responses to bradykinin was investigated. Bradykinin-binding antibodies were obtained from rabbits injected with bradykinin coupled to ovalbumin. Pre- and post-immunization sera were tested for their capacity to bind intrinsically labeled ¹⁴C-bradykinin. Six injected rabbits produced bradykinin-binding antibodies. The binding ofa radio-iodotyrosine analog of bradykinin to antiserum was inhibited by unlabeled bradykinin or kallidin, but was unaffected by oxytocin, vasopressin or angiotensin.Incubation of bradykinin with antiserum resulted in an inhibition of its hypotensive activity in the rat. Bradykinin-induced hypotension was also abolished in rats injected with antiserum. Pre-immunization serum was ineffective in both respects. Bradykinin binding antibodies also inhibited the oxytocic activity of bradykinin on the isolated rat's uterus. The inhibitory effects became evident after dialysis of the antiserum. Undialyzed antisera contained an oxytocic substance which masked the inhibition of bradykinin activity.Inhibition of pharmacological effects of bradykinin by antibradykinin was reversed by heat inactivation of antibodies. Bradykinin-binding antibodies not only inhibited bradykinin activity, but also protected the peptide against kininases.     

Pharmacological characterization of a new highly potent B2 receptor antagonist (HOE 140: D-Arg-[Hyp3,Thi5,D-Tic7,Qic8]bradykinin).

HOE 140 (D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]bradykinin), a new B2 antagonist, was compared to R-493 (D-Arg[Hyp3-D-Phe7,Leu8]bradykinin) with respect to inhibition of the responses of seven isolated smooth muscle preparations to bradykinin. R-493 was found to exert: (a) high antagonistic activity on the rabbit jugular vein (pA2 of 8.86), (b) moderate activity on the rabbit aorta, guinea-pig ileum, hamster urinary bladder and human urinary bladder (pA2 of 5.76, 6.77, 7.16 and 7.15, respectively) and (c) a stimulatory effect on the guinea-pig trachea. On the other hand, HOE 140 showed identical apparent affinities (8.36-9.12) on all preparations except the rabbit aorta where it was inactive and the guinea-pig trachea where the compound was an antagonist (pA2: 7.42) without agonistic effect. HOE 140 is specific and selective for B2 receptors since it was inactive against angiotensin II, substance P, neurokinin A, desArg9-bradykinin, noradrenaline or acetylcholine in the various preparations. R-493 inhibited the contractile effects of bradykinin competitively, while HOE 140 was not competitive even at low concentrations (7.7 x 10(-9) M). These results demonstrate that HOE 140 is a potent B2 antagonist with high affinity, specific for kinin receptors and selective for the B2 receptor type, but is non-competitive. HOE 140 is the first bradykinin receptor antagonist that acts as such on the guinea-pig trachea without showing any agonistic activity.     

Evidence for bradykinin mediation of carrageenin-induced inflammatory pain: a study using kininogen-deficient Brown Norway Katholiek rats

Inflammatory pain was induced following an intradermal injection of carrageenin into rat paws, and the hyperalgesia was measured in terms of withdrawal time following thermal pain stimulation of the inflamed paw. This hyperalgesia was significantly less in kininogen-deficient Brown Norway (B/N)-Katholiek rats, which also showed less swelling in carrageenin-induced paw edema, than in normal B/N-Kitasato rats at 1 approximately 4 hr after the carrageenin injection (at the early phase). However, 24 hr after the injection, hyperalgesia and the swelling volume of the kininogen-deficient rats were almost the same as those in normal rats. The bradykinin B2 receptor antagonist FR173657, (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolinyl)oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide, attenuated the carrageenin-induced swelling and hyperalgesia of the normal rats at the early phase to almost the levels of the B/N-Katholiek rats. Pretreatment with indomethacin, a cyclooxygenase inhibitor, also inhibited the carrageenin-induced responses significantly in normal rats. These results indicate that bradykinin, acting on the B2 receptor, is the main mediator at the early phase of inflammatory pain of carrageenin edema and that prostaglandins, produced by cyclooxygenase, potentiate the effects of bradykinin.     

BRADYKININ MEDIATES MYOCARDIAL ISCHAEMIC PRECONDITIONING AGAINST FREE RADICAL INJURY IN GUINEA-PIG ISOLATED HEART

1. Myocardial ischaemic preconditioning (IP) against free radical injury and its possible mediator(s) was investigated in a Langendorff-perfused guinea-pig heart . 2. l,l-Diphenyl-2-picryl-hydrazyl (DPPH) was used for triggering free radical injury in cardiac tissue. It reduced left ventricular developed pressure (LVDP), +dp/dt_max, heart rate (HR) and coronary flow (CF) and increased thiobarbituric acid-reactive substances (TBARS) in cardiac tissue . 3. Ischaemic preconditioning (5min global ischaemia and 5min reperfusion) exerted cardioprotection against DPPH-induced functional impairment, with significant improvement in LVDP, +dp/dt_max, HR and CF. The formation of TBARS in cardiac tissue was reduced. Blockade of bradykinin (BK) B₂ receptors with icatibant (HOE 140) abolished the cardioprotective effects of IP. 4. Bradykinin (10^?7 mol/L) perfusion for 10 min protected the heart against free radical injury. The cardioprotection induced by BK was reversed by HOE 140 . 5. Pretreatment with IP and BK results in cardiac protection against free radical injury through the activation of Bi receptors. Endogenously generated BK may mediate IP in the guinea-pig heart.