15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and icatibant

The vascular kallikrein-kinin system contributes to about one third of flow-dependent dilation in mice carotid arteries, by activating bradykinin B2 receptors coupled to endothelial nitric oxide (NO) release. Because the bradykinin/NO pathway may mediate some of the effects of angiotensin II AT2 receptors, we examined the possible contribution of AT2 receptors to the kinin-dependent response to flow. Changes in outer diameter after increases in flow rate were evaluated in perfused arteries from wild-type animals (TK+/+) and in tissue kallikrein-deficient mice (TK-/-) in which the presence of AT2 receptor expression was verified. Saralasin, a nonselective angiotensin II receptor antagonist, impaired significantly flow-induced dilation in TK+/+, whereas it had no effect in TK-/- mice. In both groups, blockade of AT1 receptors with losartan or candesartan did not affect the response to flow. Inhibition of AT2 receptors with PD123319 reduced significantly flow-induced dilation in TK+/+ mice, but had no significant effect in TK-/- mice. Combining PD123319 with the bradykinin B2 receptor antagonist HOE-140 had no additional effect to AT2 receptor blockade alone in TK+/+ arteries. Flow-dependent-dilation was also impaired in AT2 receptor deficient mice (AT2-/-) when compared with wild-type littermates. Furthermore, HOE-140 significantly reduced the response to flow in the AT2+/+, but not in AT2-/- mice. In conclusion, this study demonstrates that the presence of functional AT2 receptors is necessary to observe the contribution of the vascular kinin-kallikrein system to flow-dependent dilation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Angiotensin II Type 1 Receptor Blockers; Angiotensin II Type 2 Receptor Blockers; Animals; Benzimidazoles; Biphenyl Compounds; Bradykinin; Bradykinin B2 Receptor Antagonists; Carotid Arteries; Hemorheology; Imidazoles; Losartan; Male; Mesenteric Arteries; Mice; Mice, Inbred C57BL; Mice, Knockout; Phenylephrine; Pyridines; Receptor, Angiotensin, Type 2; Receptor, Bradykinin B2; Tetrazoles; Tissue Kallikreins; Vasodilation; Vasodilator Agents

The effects of bradykinin and the bradykinin B(2) receptor antagonists D-Arg-[Hyp(3),Thi(5,8),D-Phe(7)]-bradykinin (NPC 349) and D-Arg-[Hyp(3),Thi(5),D-Tic(7),Oic(8)]-bradykinin (Hoe 140) were examined in the electrically-stimulated rat vas deferens. Cumulative additions of bradykinin (1-3000 nM) produced two distinct responses: an enhancement in the magnitude of the basal electrically-induced twitch response (neurogenic response) and an increase in the baseline tension (musculotropic response). NPC 349 (10-100 microM) produced concentration-dependent surmountable rightward shifts of both the bradykinin neurogenic and musculotropic response curves. In contrast, while Hoe 140 (10-100 nM) caused an apparently surmountable antagonism of the bradykinin neurogenic response, it caused an apparent insurmountable antagonism of the bradykinin musculotropic response. Interestingly, co-incubation of Hoe 140 (30 nM) with NPC 349 (30 and 100 microM) resulted in a concentration-related upwards displacement of the Hoe 140-suppressed bradykinin musculotropic response curve. Thus, Hoe 140 can be described as a pseudo-irreversible antagonist against the bradykinin musculotropic response. No time-dependent changes were observed in the maximum bradykinin musculotropic response attainable when NPC 349 (100 microM) additions were made for the final 2 or 18 min of the Hoe 140 incubation (20 min). These findings indicate that slow reversibility of Hoe 140 from the bradykinin B(2) receptor is unlikely to be the mechanism responsible for the pseudo-irreversible antagonism of the bradykinin-induced musculotropic response. Instead, we propose an alternative explanation involving a third, unstable and inactive form of the bradykinin B(2) receptor.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Angiotensin II; Animals; Bradykinin; Bradykinin Receptor Antagonists; Dose-Response Relationship, Drug; Electric Stimulation; In Vitro Techniques; Male; Muscle Contraction; Muscle, Smooth; Norepinephrine; Rats; Rats, Wistar; Vas Deferens

1. The aim of this study was to assess whether the protective effect of ischaemic preconditioning on endothelial function in coronary arteries of the rat involves kinins. 2. Isolated hearts of the rat were exposed to a 30-min low-flow ischaemia (flow rate of 1 ml min[-1]) followed by 20-min reperfusion, after which coronaries were precontracted with 0.1 microM U-46619, and the response to the endothelium-dependent vasodilator, 5-hydroxytryptamine (5-HT, 10 microM), compared to that of the endothelium-independent vasodilator, sodium nitroprusside (SNP, 3 microM). 3. In untreated hearts, ischaemia-reperfusion diminished selectively 5-HT-induced vasodilatation, compared with time-matched sham hearts. The vasodilatation to SNP was unaffected after ischaemia-reperfusion. Preconditioning (5 min of zero-flow ischaemia followed by 10 min reperfusion) in untreated hearts preserved the vasodilatation produced by 5-HT. 4. Blockade of B1 and B2 receptors with either 3 nM [Lys[0], Leu8, des-Arg9]-bradykinin (LLDBK) or 10 nM Hoe 140 (icatibant), respectively, (started 15 min before ischaemic preconditioning or a corresponding sham period and stopped just before the 20-min reperfusion period) had no effect on the vasodilatation produced by either 5-HT or SNP in sham hearts. Pretreatment with Hoe 140 did not block the protective effect of ischaemic preconditioning on the 5-HT vasodilatation. In contrast, LLDBK halved the protective effect of ischaemic preconditioning on endothelium-dependent vasodilatation. 5. Perfusion with either bradykinin or des-Arg9-bradykinin (1 nM) 30 min before and lasting throughout the ischaemia protected the endothelium. 6. In conclusion, ischaemic preconditioning affords protection to the endothelial function in coronary resistance arteries of the rat partly by activation of B1 receptors. Although exogenous BK perfusion can protect the endothelium, B2 receptors do not play an important role in this protection in the rat isolated heart.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Bradykinin; Bradykinin Receptor Antagonists; Endothelium, Vascular; Heart; Ischemic Preconditioning; Kinins; Male; Myocardial Ischemia; Rats; Rats, Sprague-Dawley; Vascular Resistance

We previously demonstrated that the bradykinin-induced contraction of human isolated small bronchi is inhibited by indomethacin, capsaicin (N-methyl-N-6-nonenamide) and ruthenium red but not by tachykinin receptor antagonists. The thromboxane A2 receptor (TP receptor) antagonist GR32191 ((1R-(1 alpha(Z),2 beta,3 beta,5 alpha))-(+)-7-(5-(((1,1'-biphenyl)-4-yl)- methoxy)-3-hydroxy-2-(1-piperidinyl)cyclopentyl)-4-heptenoic acid, hydrochloride) (10(-10) to 10(-8) M) dose dependently inhibited the effect of bradykinin, suggesting the mediation of the TP receptor in the action of bradykinin. With higher concentrations of GR32191 (10(-7) and 10(-6) M) bradykinin induced a relaxation which was inhibited by indomethacin and by the bradykinin B2 receptor antagonist Hoe 140 (D-Arg0[Hyp3,Thi-5,D-Tic7,Oic8]bradykinin). The thromboxane A2 synthase inhibitor dazoxiben (4-(-2-(1H-imidazol-1-yl)ethoxy) benzoic acid hydrochloride) 10(-6) M inhibited the bradykinin-induced contraction, suggesting that thromboxane A2 was involved in TP receptor stimulation. The thromboxane A2 mimetic U-46619 (9,11-dideoxy-11 alpha,9 alpha-epoxy-methano-prostaglandin F2 alpha)-induced contraction of human distal bronchi was not inhibited by capsaicin and ruthenium red. Our data suggest that bradykinin contracts human isolated small bronchi through thromboxane A2 release. The inhibitory effect of ruthenium red and capsaicin on the bradykinin response may be due to inhibition of thromboxane A2 release or arachidonic mobilisation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adult; Aged; Biphenyl Compounds; Bradykinin; Bronchi; Capsaicin; Dose-Response Relationship, Drug; Heptanoic Acids; Humans; Imidazoles; Indomethacin; Male; Middle Aged; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Prostaglandin Endoperoxides, Synthetic; Receptors, Thromboxane; Ruthenium Red; Thromboxane A2; Thromboxane-A Synthase; Vasoconstrictor Agents

The effect of bradykinin (BK) on the contraction of rat mesangial cells (MC) was compared with that of various vasoactive agents. BK induced a dose-dependent contraction [one-half maximal effective dose (ED50) = 50 nM] inhibited by the B2 antagonist, HOE-140 (ED50 = 10 nM). BK-induced MC contraction was independent of extracellular calcium and was reduced by inhibition of protein kinase C (PKC). Neomycin completely prevented the increase in intracellular calcium and the formation of inositol 1,4,5-trisphosphate induced by BK but only reduced cell contraction. Inhibition of prostaglandin (PG) formation and administration of the endoperoxide antagonist SQ-27427 also partly decreased the effect of BK. Interestingly, only the addition of both neomycin and mepacrine resulted in a complete inhibition of cell contraction. These results suggest that BK, via a B2-kinin receptor, induces contraction of MC through two distinct mechanisms, one associated to the phospholipase C pathway and subsequent activation of PKC and the second one dependent on PG formation. These in vitro effects may be relevant in explaining the effects of BK and converting enzyme inhibitors on glomerular hemodynamics.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adrenergic beta-2 Receptor Antagonists; Angiotensin II; Animals; Arginine Vasopressin; Bombesin; Bradykinin; Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cell Membrane; Cells, Cultured; Dinoprost; Dinoprostone; Dose-Response Relationship, Drug; Endothelins; Fatty Acids, Unsaturated; Glomerular Mesangium; Indomethacin; Kinetics; Naphthalenes; Neomycin; Polycyclic Compounds; Prostaglandin Endoperoxides, Synthetic; Protein Kinase C; Quinacrine; Rats; Receptors, Adrenergic, beta-2; Surface Properties; Tetradecanoylphorbol Acetate; Thromboxane A2; Vasoconstrictor Agents

The inhibitory effects of HOE 140, a novel bradykinin B2 receptor antagonist, on pulmonary vascular and airway responses to bradykinin (BK) were investigated under conditions of controlled pulmonary blood flow and ventilation and constant left atrial pressure in the isolated blood-perfused rat lung. Under baseline conditions, BK produced dose-related increases in pulmonary arterial perfusion pressure without changing airway pressure. However, when pulmonary arterial pressure was raised to a high steady level, increases in pulmonary arterial pressure in response to BK were enhanced and BK then produced dose-related increases in airway pressure. Responses to BK were reproducible with respect to time and were not different when the inspired fraction of O2 was 0.21 or 0.95 and HOE 140 was 0.8 nM/ml (50 micrograms/kg) and decreased both pulmonary vascular and airway responses to the peptide. HOE 140 had no significant effect on pulmonary vascular responses to angiotensin II, serotonin, nitric oxide, sodium nitroprusside, albuterol, or pinacidil. Additionally, in these experiments, HOE 140 had no effect on the pulmonary arterial pressor response to ventilatory hypoxia. These results suggest BK has significant vasoconstrictor and bronchoconstrictor effects that are mediated by B2 receptors and are dependent on the baseline level of tone in the airways and in the pulmonary vascular bed. The present results suggest that HOE 140 is a highly selective, BK B2 receptor antagonist in the pulmonary vascular bed of the rat. These data also suggest that HOE 140 may be a useful probe for studying the role of BK in the pulmonary vascular bed in physiological and pathophysiological conditions.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Arginine; Blood Pressure; Bradykinin; Captopril; In Vitro Techniques; Lung; Male; Meclofenamic Acid; NG-Nitroarginine Methyl Ester; Oxygen; Perfusion; Prostaglandin Endoperoxides, Synthetic; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Respiration; Thromboxane A2

This study investigates the mechanisms involved in kinin-induced contractions in rings of rat portal vein (RPV). Bradykinin (BK), Lys-BK, Met-Lys-BK, Tyr8-BK (TBK) and des-Arg9-BK (DABK) all caused graded contractions in RPV, with the following order of potency (EC50, nanomolar): Met-Lys-BK (0.3) > Lys-BK (0.5) > BK (0.9) > TBK (2.3) >> DABK (46.0). The potency of DABK and maximal contractions for DABK and BK, but not for TBK or NE, increased as a function of in vitro incubation period, reaching the maximum at 4.5 hr. Cycloheximide (a protein synthesis inhibitor, 70 microM), incubated for 4.5 hr, inhibited almost completely the CRCs for DABK and blocked the latter phase of CRCs for BK, not altering contractions induced by U46619 (9,11-dideoxy-9 alpha, 11 alpha-methano-epoxy prostaglandin F2 alpha) (a thromboxane A2/prostaglandin H2-mimetic). Incubation of RPV with D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-BK (HOE 140, a selective B2 receptor antagonist, 0.01-100 nM), caused a parallel rightward displacement of the BK and TBK concentration-response curves (CRCs). Schild plots were linear, yielding pA2 values of 11.4 and 9.3, respectively. The slope for HOE 140 against TBK-induced contractions did not differ from unity (1.23 +/- 0.21), whereas against BK was significantly lesser than unity (0.72 +/- 0.20). The CRCs induced by DABK were not affected by HOE 140 (100 nM). In addition, the CRCs for DABK at 4.5 hr were shifted to the right in a parallel form in the presence of des-Arg9-[Leu8]-BK (a selective B1-receptor antagonist, 1 microM), yielding a pA2 value of 6.7.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Bradykinin; Cycloheximide; Dose-Response Relationship, Drug; Imidazoles; In Vitro Techniques; Indoles; Male; Norepinephrine; Portal Vein; Prostaglandin Endoperoxides, Synthetic; Rats; Rats, Wistar; Receptors, Bradykinin; Thromboxane A2; Vasoconstriction