thromboxane-a2 and ramatroban

COPD (Chronic Obstructive Pulmonary Disease) and bronchial asthma are two severe lung diseases which represent a major problem of world public health. Leukotrienes and prostanoids play an important role in the pathogenesis of pulmonary diseases. Prostanoids: prostaglandins (PGs) and thromboxane A2 (TXA2), the cyclooxygenase metabolites of arachidonic acid are implicated in the inflammatory cascade that occurs in asthmatic airways. Recently, the roles played by isoprostanes or prostaglandin-like compounds nonenzymatically generated via peroxidation of membrane phospholipids by reactive oxygen species, in particular F2-isoprostanes, in pulmonary pathophysiology have been highlighted. This article aims to provide an overview of the role of prostanoids and isoprostanes in the pathogenesis of COPD and asthma and to discuss the pharmacological strategies developed in prevention and/or treatment of these pathologies.

Topics: Animals; Asthma; Benzoquinones; Carbazoles; Enzyme Inhibitors; F2-Isoprostanes; Heptanoic Acids; Humans; Methacrylates; Prostaglandin Antagonists; Prostaglandin D2; Pulmonary Disease, Chronic Obstructive; Randomized Controlled Trials as Topic; Receptors, Immunologic; Receptors, Prostaglandin; Receptors, Thromboxane A2, Prostaglandin H2; Sulfonamides; Thromboxane A2; Thromboxane-A Synthase

Bronchial asthma is a disease defined by reversible airway obstruction, bronchial hyperresponsiveness and inflammation. In addition to histamine and acetylcholine, recent studies have emphasized the role of arachidonic acid metabolites (leukotrienes, prostaglandins and thromboxane A(2)) in the pathogenesis of asthma. Among these mediators, thromboxane A(2) (TXA(2)) has attracted attention as an important mediator in the pathophysiology of asthma because of its potent bronchoconstrictive activity. Thromboxane A(2) is believed to be involved not only in late asthmatic responses but also in bronchial hyperresponsiveness, a typical feature of asthma. Strategies for inhibition of TXA(2) include TXA(2) receptor antagonism and thromboxane synthase inhibition. Results of double-blind, placebo-controlled clinical trials have proven the efficacies of the thromboxane receptor antagonist seratrodast and the thromboxane synthase inhibitor ozagrel in the treatment of patients with asthma. Seratrodast and ozagrel are available in Japan for the treatment of asthma. Ramatroban, another thromboxane receptor antagonist, is currently under phase III clinical evaluation in Europe and Japan for the treatment of asthma. The pharmacological profiles of the thromboxane modulators may be improved by combination with leukotriene D(4) receptor antagonists. A multi-pathway inhibitory agent such as YM 158, which is a novel orally active dual antagonist for leukotriene D(4) and thromboxane A(2 )receptors, may have potent therapeutic effects in the treatment of bronchial asthma. Large scale clinical trials are necessary to further define the role of thromboxane modulators in the treatment of patients with asthma.

Topics: Anti-Asthmatic Agents; Asthma; Benzoquinones; Carbazoles; Heptanoic Acids; Humans; Methacrylates; Molecular Structure; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Thromboxane-A Synthase

Lung tissues produce a large amount of Thromboxane (Tx) A2. In addition to platelet aggregation and artery smooth muscle contraction, TxA2 strongly induces airway smooth muscle contraction and bronchial hyperresponsiveness. Not only TxA2, but many arachidonate cyclooxygenase metabolites such as PGD2, PGF2 alpha, PGH2, and others stimulate TP (PGH2/TxA2) receptor and can take a pathophysiological role for bronchial asthma. Several compounds competitively antagonizing TP receptor have been developed and being proved to have beneficial effects for treating of bronchial asthma in clinical. In this review the efficacy and usage of TP receptor antagonists for bronchial asthma was discussed.

Topics: Asthma; Benzoquinones; Bridged Bicyclo Compounds; Bronchi; Bronchial Hyperreactivity; Carbazoles; Fatty Acids, Monounsaturated; Heptanoic Acids; Humans; Prostaglandins; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

It has been considered that thromboxane A2 (TXA2) is involved in the development of bronchial hyperresponsiveness (BHR), a characteristic feature of asthma. To ensure the involvement of TXA2 in BHR of asthma, effects of a 1-week treatment with two orally active TXA2 antagonists, BAY u 3405 and S-1452, on BHR were examined in 10 and 13 patients with stable asthma, respectively, in two consecutive double-blinded, randomized, placebo-controlled, two-phase crossover studies. Provocative concentration of methacholine causing a 20% fall in FEV1 (PC20-FEV1) with BAY u 3405 (0.78 (GSEM, 1.50) mg/ml) was significantly greater than the value with placebo (0.65 (GSEM, 1.46) mg/ml) (ratio 1.23 times, 95% CI 1.01 to 1.46: P = 0.0401). PC20-FEV1 was also significantly increased with S-1452 (0.43 (GSEM, 1.39) mg/ml) compared with placebo (0.29 (GSEM, 1.27) mg/ml) (ratio 1.75 times, 95% CI 1.05 to 2.45: P = 0.0189). Baseline pulmonary function was not altered by these treatments. These results may ensure that TXA2 is significantly involved in the BHR of asthma while the degree of contribution may be small.

Topics: Adolescent; Adult; Airway Resistance; Asthma; Bridged Bicyclo Compounds; Bronchial Hyperreactivity; Bronchoconstrictor Agents; Carbazoles; Cross-Over Studies; Double-Blind Method; Fatty Acids, Monounsaturated; Female; Forced Expiratory Volume; Humans; Male; Methacholine Chloride; Middle Aged; Prostaglandin Antagonists; Sulfonamides; Thromboxane A2

Twelve patients with Dacron aortic grafts participated in a placebo controlled, crossover trial to investigate the effect of Bay u3405, a thromboxane A2 receptor antagonist, on graft thrombogenicity. During each treatment period (seven days, Bay u3405 or placebo), 111In-platelet survival and platelet deposition on the grafts were measured daily by gamma-camera imaging and blood radioactivity analysis. Bay u3405 substantially reduced the deposition of platelets and the thrombogenic index, while platelet survival remained unchanged. The ex vivo platelet aggregation response to ADP and epinephrine was significantly inhibited. The bleeding time increased slightly but not to any clinically relevant extent, and no adverse side effects were recorded. Bay u3405 seems to be a safe and effective drug for the inhibition of platelet deposition on aortic Dacron grafts. The use of quantitative imaging techniques is also more sensitive than the measurement of platelet survival for the assessment of antiplatelet drug efficacy in patients with aortic grafts.

Topics: Aged; Aorta; Blood Platelets; Blood Vessel Prosthesis; Carbazoles; Cell Survival; Double-Blind Method; Follow-Up Studies; Humans; Indium Radioisotopes; Male; Middle Aged; Platelet Adhesiveness; Polyethylene Terephthalates; Sulfonamides; Thromboxane A2

Thromboxane (TxA. Using isolated organ bath, saphenous vein and internal mammary artery preparations were incubated with TP receptor antagonist, TxS inhibitor, aspirin, IP or EP4 receptor antagonist. Then prostaglandin (PG)E. TP receptor antagonist and TxS inhibitor are more effective to reduce contraction induced by different spasmogens in comparison to aspirin. Our results suggest that TP receptor antagonist and TxS inhibitor might have an advantage over aspirin due to their preventive effect on increased vascular reactivity observed in post-operative period of coronary artery bypass grafting.

Topics: Arachidonic Acid; Aspirin; Benzofurans; Carbazoles; Enzyme Inhibitors; Female; Humans; Male; Mammary Arteries; Muscle, Smooth, Vascular; Phenylephrine; Receptors, Prostaglandin; Receptors, Thromboxane; Saphenous Vein; Sulfonamides; Thromboxane A2; Thromboxane-A Synthase; Thromboxanes; Vasoconstriction

The aim of this study was to investigate the involvement of chemical mediators in a nasal congestion model in Brown Norway (BN) rats. For the above purpose, we studied the effects of pranlukast and zafirlukast (cysteinyl leukotriene (cys-LT) receptor antagonists), seratrodast and ramatroban (thromboxane A(2) (TXA(2)) receptor antagonists) on nasal congestion and sneezing induced by toluene 2, 4-diisocyanate (TDI). All of these drugs suppressed the increase of enhanced pause (Penh), the index of nasal congestion, in both early and late phase responses; however, pranlukast, zafirlukast and seratrodast failed to suppress immediate sneezing caused by TDI challenge. These results indicate that cys-LTs and TXA(2) are responsible for the development of both early and late phase nasal congestion. Moreover, these chemical mediators contribute very little to immediate sneezing in a BN rat model of allergic rhinitis.

Topics: Animals; Benzoquinones; Carbazoles; Chromones; Dose-Response Relationship, Drug; Heptanoic Acids; Indoles; Leukotrienes; Male; Membrane Proteins; Phenylcarbamates; Rats; Rats, Inbred BN; Receptors, Leukotriene; Receptors, Thromboxane A2, Prostaglandin H2; Rhinitis; Sneezing; Sulfonamides; Thromboxane A2; Tosyl Compounds

The aim of this study was to characterize the in vivo pharmacokinetics with the enterohepatic circulation (EHC) and identify the role of multidrug resistance-associated protein 2 (MRP2/Mrp2) in biliary excretion and absorption of ramatroban, a thromboxane A2 antagonist using a recirculatory model.. Ramatroban was intravenously or orally administered to Sprague-Dawley rats (SDR) and Eisai hyperbilirubinemic rats (EHBR). Portal and systemic blood and bile samples were collected, and the drug concentrations were analyzed by high-performance liquid chromatography (HPLC) to estimate various global and local moments.. The bioavailability (BA) of ramatroban was estimated at 21.0% in SDR and 61.9% in EHBR. The local absorption ratio for the dosage after oral administration (Fa(dosage)) and the single-pass local absorption ratio for EHC (Fa') in the rats were similar and nearly 100%. The hepatic recovery ratio (Fh) and the single-pass biliary excretion ratio through the liver for the sum of ramatroban and its glucuronides (Fb) in EHBR were 61.4% and 8.88%, respectively, which differed considerably from those in SDR (15.0% and 22.4%). The difference in hepatic elimination between these strains would be caused, at least in part, by the reduced biliary excretion in EHBR, although the biliary excretion was not completely impaired.. Ramatroban may be excreted by multiple transport systems, followed by efficient enterohepatic reabsorption in both strains. The results suggest that ramatroban may not be susceptible to drug-drug interaction involving MRP2/Mrp2 in biliary excretion and absorption.

Topics: Administration, Oral; Animals; Animals, Genetically Modified; Bile; Carbazoles; Disease Models, Animal; Enterohepatic Circulation; Glucuronides; Hyperbilirubinemia; Injections, Intravenous; Membrane Transport Proteins; Metabolic Clearance Rate; Multidrug Resistance-Associated Protein 2; Multidrug Resistance-Associated Proteins; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane A2, Prostaglandin H2; Species Specificity; Sulfonamides; Thromboxane A2

The purpose of this study was to investigate the involvement of chemical mediators other than histamine in nasal allergic signs using histamine H(1) receptor-deficient mice. In passively sensitized mice, antigen instillation into the nasal cavity induced significant increases in sneezing and nasal rubbing in wild-type mice, but no such increases were observed in histamine H(1) receptor-deficient mice. In actively sensitized mice, both sneezing and nasal rubbing were also significantly increased in a dose-dependent manner in both wild-type and histamine H(1) receptor-deficient mice. Histamine H(1) receptor antagonists such as cetirizine and epinastine significantly inhibited antigen-induced nasal allergic signs in wild-type mice, although the effects were incomplete. In addition, the thromboxane A(2) receptor antagonist ramatroban also inhibited these responses in wild-type mice. However, the leukotriene receptor antagonist zafirlukast showed no effects in wild-type mice. These results suggested that in the acute allergic model (passive sensitization), only histamine H(1) receptors are related to nasal signs induced by antigen, whereas in the chronic allergic model (active sensitization), both histamine H(1) receptors and thromboxane A(2) receptors were involved in the responses.

Topics: Animals; Anti-Allergic Agents; Antigens; Behavior, Animal; Carbazoles; Cetirizine; Dose-Response Relationship, Drug; Female; Histamine H1 Antagonists; Immunization; Immunoglobulin E; Indicators and Reagents; Indoles; Leukotriene Antagonists; Mice; Mice, Knockout; Ovalbumin; Passive Cutaneous Anaphylaxis; Phenylcarbamates; Receptors, Histamine H1; Rhinitis, Allergic, Seasonal; Sneezing; Sulfonamides; Thromboxane A2; Tosyl Compounds

To investigate the crucial role of platelet-derived thromboxane A(2) (TXA(2)) in initiating Ag-specific contact sensitivity (CS), a platelet-dependent CS model using genetically mast cell-deficient W/W(v) mice, was provided. In vivo treatment with BAYu3405, a TXA(2) receptor antagonist, markedly suppressed CS responses in a dose-dependent manner. This inhibitory effect occurred when BAYu3405 was administered before an early initiating phase, suggesting that TXA(2) may be a potent initiator of platelet-mediated CS responses. When platelets were pretreated with BAYu3405 in vitro, platelet aggregation as well as serotonin release, which is able to induce the early phase response allowing local recruitment of CS effector T cells due to direct activation of vascular endothelial cells, was inhibited. The addition of U46619, a TXA(2) agonist, or a mixture of platelets and thrombin-enhanced expression of both ICAM-1 and VCAM-1 on isolated mouse aortic endothelial cells, which was completely abolished by pretreatment with BAYu3405. Furthermore, intradermal injection of U46619 into the ear of platelet-depleted mice led to CS responses with marked expression of ICAM-1 and VCAM-1 on the vascular endothelium. These findings suggest that TXA(2) generated from platelets activated with Ag may mediate initiation of CS responses through inducing serotonin release from platelets and the subsequent aggregation and up-regulated expression of ICAM-1 and VCAM-1 on vascular endothelial cells.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Triphosphate; Animals; Aorta, Abdominal; Aorta, Thoracic; Blood Platelets; Carbazoles; Cells, Cultured; Dermatitis, Contact; Ear; Endothelium, Vascular; Humans; Immune Sera; Injections, Intradermal; Injections, Intraperitoneal; Injections, Intravenous; Intercellular Adhesion Molecule-1; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Platelet Activation; Platelet Aggregation Inhibitors; Receptors, Thromboxane; Serotonin; Sulfonamides; Thromboxane A2; Vascular Cell Adhesion Molecule-1; Vasoconstrictor Agents

Isolated smooth muscle cells from the small intestine of new-born rats were prepared by enzymatic digestion. These cells re-aggregate after 1 day in culture to clusters. The re-aggregates show spontaneous rhythmical contractions at 37 degrees C with a frequency (13.1 +/- 0.8 min-1, n = 49), which is similar to that of the intact smooth muscle layer. The cholinergic agonist carbachol (5 x 10(-5) mol l-1) caused an increase in the frequency of the spontaneous contractions often ending in a permanent contraction. A similar effect was achieved with the thromboxane A2 (TXA2) agonist, U-46619 (10(-5) mol l-1). In contrast, both the TXA2 receptor blocker, Bay u3405 (5 x 10(-4) mol l-1), as well as the Ca2+ channel blocker, verapamil (5 x 10(-5) mol l-1), suppressed the spontaneous contractions. The observed contractility was insensitive against the neuronal blocker tetrodotoxin (10(-6) mol l-1). These analyses of video images were supported by the measurement of relative changes in the intracellular Ca2+ concentration with the Ca(2+)-sensitive dye, fura-2. Spontaneous contractions were paralleled by spikes in the intracellular Ca2+ concentration, which were abolished by Bay u3405, but stimulated by U-46619 or carbachol. In summary, these results obtained at re-aggregates of intestinal smooth muscle cells support the hypothesis of a role of TXA2 in the generation of spontaneous intestinal smooth muscle contractions in vitro.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Animals, Newborn; Calcium; Carbachol; Carbazoles; Cell Aggregation; Cholinergic Agonists; Fluorescent Dyes; Fura-2; Intestine, Small; Microscopy, Fluorescence; Muscle Contraction; Muscle, Smooth; Platelet Aggregation Inhibitors; Rats; Sulfonamides; Tetrodotoxin; Thromboxane A2; Vasoconstrictor Agents; Verapamil

The effect of inhibitors of the thromboxane A2 pathway on spontaneous contractions of intestinal smooth muscle preparations was studied. The thromboxane A2 antagonists Bay u3405, SK and F 88046 and KW-3635 concentration-dependently inhibited both the amplitude and the frequency of spontaneous contractions of the longitudinal muscle from the rat proximal colon. A concentration-dependent inhibition of the myogenic contractions was also observed with the thromboxane A2 synthase inhibitor U-51605, and with the combined cyclooxygenase/lipoxygenase inhibitor nordihydroguaiaretic acid, whereas indomethacin, a pure cyclooxygenase inhibitor, was ineffective. None of these inhibitors affected the contractile response evoked by the cholinergic agonist carbachol, excluding non-specific actions on intestinal motility. A similar response was observed for the rabbit jejunum, which, in contrast to the rat colon, exhibits more regular, high-frequency spontaneous contractions, which were inhibited by Bay u3405, SK and F 88046 and KW-3635 in a concentration-dependent manner, whereas the response to carbachol remained unaffected. These results suggest a role for thromboxane A2 in the generation and/or facilitation of spontaneous smooth muscle contractions in the gut.

Topics: Animals; Benzimidazoles; Benzoxepins; Carbachol; Carbazoles; Colon; Female; In Vitro Techniques; Indomethacin; Intestine, Small; Isometric Contraction; Male; Masoprocol; Muscle, Smooth; Rabbits; Rats; Rats, Wistar; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

8-Epi-prostaglandin F2alpha (8-epi-PGF2alpha) is an F2-isoprostane formed mainly via noncyclooxygenase pathways in vivo. We investigated whether 8-epi-PGF2alpha has any effect on airflow obstruction and plasma exudation in vivo. Airflow obstruction was quantified by measuring lung resistance (RL) in anesthetized and ventilated guinea pigs, and plasma exudation was quantified by the Evans Blue dye method (20 mg/kg intravenously). Intratracheal instillation of 8-epi-PGF2alpha (1 nmol or 10 nmol) caused dose-related increases in RL. Furthermore, the higher dose of 8-epi-PGF2alpha produced Evans Blue dye extravasation in main bronchi and intrapulmonary airways. A prostanoid TP-receptor antagonist, BAY u3405 (1 mg/kg intravenously), abolished the airway effects of 8-epi-PGF2alpha (10 nmol). A thromboxane A2 (TxA2) synthase inhibitor, OKY-406 (30 mg/kg intravenously), significantly attenuated these effects of 8-epi-PGF2alpha (10 nmol). The level of TxB2, a stable TxA2 metabolite, increased in bronchoalveolar lavage fluid (BALF) after 8-epi-PGF2alpha instillation. We conclude that 8-epi-PGF2alpha causes airflow obstruction and plasma exudation in vivo. This effect may be mediated primarily via prostanoid TP-receptors, and a secondary generation of TxA2 may be involved in part of the airway responses in 8-epi-PGF2alpha in the guinea pig.

Topics: Airway Obstruction; Animals; Bronchoalveolar Lavage Fluid; Carbazoles; Dinoprost; Guinea Pigs; Histamine Antagonists; Male; Methacrylates; Platelet Aggregation Inhibitors; Sulfonamides; Thromboxane A2; Thromboxane B2; Vasoconstrictor Agents

The absorption, concentrations in plasma, metabolism and excretion of ramatroban ((+)-(3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9- carbazolepropanoic acid, CAS 116649-85-5, BAY u 3405) have been studied following a single intravenous, oral, or intraduodenal administration of 14C-labeled or nonlabeled compound to rats and dogs (dose range: 1-10 mg.kg-1). After intraduodenal administration of [14C]ramatroban, enteral absorption of radioactivity was rapid and almost complete both in bile duct-cannulated male rats (83%) and female dogs (95%). The oral bioavailability of ramatroban was complete in the dog but amounted to about 50% in the rat due to presystemic elimination. A marked food effect on the rate but not on the extent of absorption was observed in rats. The elimination of the parent compound from plasma occurred rapidly with total clearance of 1.2 l.h-1.kg-1 in male rats and 0.7 l.h-1.kg-1 in dogs. After oral administration to male rats AUC increased dose-proportionally between 1 and 10 mg.kg-1, whereas in Cmax an over-proportional increase was observed. Excretion of total radioactivity was fast and occurred predominantly via the biliary/fecal route in both species. The residues were low, 144 h after dosing less than 0.2% of the radioactivity remained in the body of rats. A considerable sex difference was found in rats following oral administration of ramatroban. In females a 3-fold higher AUC and a 1.7-fold longer half-life of unchanged compound, as well as 3-fold higher renal excretion of total radioactivity was observed. A marked species difference exists in the metabolism of ramatroban. In dogs the drug was almost exclusively metabolized via conjugation with glucuronic acid, whereas in rats oxidative phase I metabolism and glucuronidation were equally important. As a consequence enterohepatic circulation was much more pronounced in dogs (77%) than in rats (17% of the initial dose).

Topics: Administration, Oral; Animals; Biological Availability; Biotransformation; Carbazoles; Chromatography, High Pressure Liquid; Dogs; Enterohepatic Circulation; Female; In Vitro Techniques; Injections, Intravenous; Intestinal Absorption; Liver; Magnetic Resonance Spectroscopy; Male; Mass Spectrometry; Rats; Rats, Wistar; Receptors, Thromboxane; Sex Characteristics; Species Specificity; Spectrophotometry, Ultraviolet; Sulfonamides; Thromboxane A2

The distribution to organs and tissues, placental transfer and mammary excretion of ramatroban ((+)- (3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9- carbazolepropanoic acid, CAS 116649-85-5, BAY u 3405) have been investigated in rats. Furthermore, the characteristics of protein binding in plasma of various species including man are described. After single oral administration of [14C]ramatroban to male rats, the radioactivity was preferentially localized in liver and kidneys, the tissue-to-plasma concentration ratios at tmax were 20 for liver and 6.3 for kidneys, respectively. For all other organs/tissues, a low to moderate affinity was detected. [14C]Ramatroban and its labeled metabolites did hardly penetrate the blood-brain barrier, and the brain-to-plasma concentration ratio was 0.03 at tmax. After repeated oral administration to male rats for 21 days, once daily, the radioactivity concentrations in organs and tissues showed only a slight tendency to accumulate. The AUC ratios in the dosing interval exhibited little or no increase, the highest accumulation factor was approximately 2. The steady-state of the trough levels in plasma was reached rapidly, with the third administration. The autoradiographic distribution pattern was not changed due to repeated administration. After receiving single oral doses of [14C]ramatroban, female rats showed almost identical autoradiographic distribution patterns of radioactivity compared with males. Although being similarly distributed, in most organs and tissues of pregnant rats (19th day of gestation) distinctly higher radioactivity concentrations were observed than in males. Maximal fetal concentrations occurred at 7 h after dosing. The distribution in fetuses was similar to that in maternal body, revealing relatively high concentrations in liver, kidneys, and gastrointestinal contents. The fetal AUC reached 68% of the AUC in maternal plasma. [14C]Ramatroban was excreted with the milk of lactating rats. The total amount within 24 h was estimated to be 1.7% of the maternal dose. [14C]Ramatroban is highly bound to plasma proteins in all species tested: rabbit (unbound fraction: 1.7-1.9%), rat (2.1-2.4%), man (2.0-2.7%), dog (2.4-2.8%), mouse (3.7-4.1%), guinea-pig (4.3-4.7%).

Topics: Administration, Oral; Animals; Area Under Curve; Autoradiography; Blood Proteins; Carbazoles; Dogs; Female; Injections, Intravenous; Male; Mice; Milk; Placenta; Pregnancy; Protein Binding; Rabbits; Rats; Rats, Wistar; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Tissue Distribution

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Bridged Bicyclo Compounds, Heterocyclic; Carbazoles; Fatty Acids, Unsaturated; Female; Humans; Hydrazines; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Muscle, Smooth, Vascular; Myometrium; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Umbilical Arteries

It has been reported that cholinergic agonists induce bronchoconstriction by directly stimulating M3 muscarinic receptors on the surfaces of smooth muscle cells. Although thromboxane A2 (TXA2) has been demonstrated to induce airway hyperresponsiveness to cholinergic agonists in vivo, it does not affect the contractile response of smooth muscle to cholinergic agonists in vitro. To investigate the causes for the discrepancy between the in vivo and in vitro data, we compared the effects exerted by a TXA2 mimetic, U-46619, on the smooth muscle of canine trachea and bronchiole. We measured the contractile response to exogenously applied acetylcholine (ACh) before and after the application of a subthreshold dose of U-46619. The subthreshold dose was determined as that dose which did not induce smooth muscle contraction, this being 10(-9) M in the present study. The contractile responses of tracheal strips to ACh were not affected by the subthreshold dose of U-46619. By contrast, the responses of bronchiolar rings were significantly enhanced by this subthreshold dose. The excitatory effect of U-46619 on the ACh-induced contraction was completely prevented by treatment with a TXA2 antagonist, BAY u3405. These results indicate that TXA2 directly increases the responsiveness of smooth muscle in the bronchiole, and suggest that increases in the responsiveness of small airways may play an important role in the development of the airway hyperresponsiveness induced by TXA2.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Animals; Bronchi; Carbazoles; Dogs; Female; Male; Muscle Contraction; Muscle, Smooth; Prostaglandin Endoperoxides, Synthetic; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Trachea; Vasoconstrictor Agents

Although the bronchoconstriction induced by leukotriene D4 (LTD4) has been reported to be partly mediated by thromboxane A2 (TXA2) in the guinea-pig airway, it is not known which part of the airway is susceptible to TXA2. In order to determine the role of TXA2 in the central and peripheral airways, we compared the effect of a TXA2 antagonist on tracheal strips to its effect on parenchymal strips of guinea-pigs. Tracheal and parenchymal strips were mounted in a 3.5 ml organ bath filled with Krebs-Henseleit solution aerated with 95% O2, 5% CO2 and kept at 37 degrees C. After equilibration for 60 min in Krebs solution, the strip was contracted by exposure to 10(-5) M of acetylcholine (ACh). Sixty minutes after ACh was eliminated, the concentration-response curve to LTD4 (10(-9) M-10(-7) M) was obtained, and the LTD4-induced contractions were expressed as the percent of the contraction evoked by 10(-5) M of ACh. We measured the contractile response to LTD4 in the presence or absence of the TXA2 antagonist, BAY u3405 (10(-8) M-10(-6) M). In the tracheal strips, BAY u3405 had no effect on the LTD4-induced contraction. However, in parenchymal strips, BAY u3405 significantly suppressed the contractile response to LTD4. These results suggest that in the central airway LTD4 contracts smooth muscle directly, but that in the peripheral airway LTD4 induces smooth muscle contraction both directly and indirectly, via TXA2.

Topics: Animals; Carbazoles; Female; Guinea Pigs; Leukotriene D4; Lung; Male; Muscle Contraction; Muscle, Smooth; Platelet Aggregation Inhibitors; Sulfonamides; Thromboxane A2; Trachea

[3H]PGE2 and [3H]PGF2 alpha were shown to bind with similar binding capacity and dissociation constants to bovine aorta endothelial cells. The similarity in the binding parameters suggests that both agonists may bind to the same binding site. Displacement of [3H]PGE2 performed with PGE2, PGF2 alpha or U-46619, a thromboxane agonist, shows that all three prostanoids displaced the bound [3H]PGE2 with comparable potency (IC50 = 10(-7) M). These results indicated that the three different prostanoids, which serve as specific agonists to different prostanoid receptors, also compete for the same binding site in bovine endothelial cells with similar affinity. Comparison of the displacement of [3H]PGE2 or [3H]PGF2 alpha by a number of prostaglandin agonists and antagonists further supports the notion that the natural prostanoids bind with similar affinities to the same binding site. Thus, sulprostone, an EP1/EP3 agonist, displaced bound [3H]PGE2 and [3H]PGF2 alpha with IC50 of about 10(-7) M. On the other hand, thromboxane antagonists (BAY u-3405 and GR-32191B), EP1 specific antagonist (SC-19220) EP1/DP antagonist (AH-6809) and iloprost, a stable prostacyclin agonist, failed to displace bound [3H]PGE2 or [3H]PGF2 alpha at a concentration range of 10(-9)-10(-6) M. Gradual increase of sodium fluoride (NaF), a general activator of G binding proteins, or incubation of permeabilized cells with GTP gamma S resulted in a decrease in [3H]PGE2 binding, suggesting that the binding site represents a low-affinity common prostanoid receptor which, similar to other prostanoid receptors, is probably coupled with G binding proteins.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aorta; Binding Sites; Biphenyl Compounds; Carbazoles; Cattle; Cells, Cultured; Dibenz(b,f)(1,4)oxazepine-10(11H)-carboxylic acid, 8-chloro-, 2-acetylhydrazide; Dinoprostone; Endothelium, Vascular; Epoprostenol; Heptanoic Acids; Iloprost; Prostaglandin Endoperoxides, Synthetic; Prostaglandins; Sulfonamides; Thromboxane A2; Thromboxanes; Xanthenes; Xanthones

Thromboxane A2 (TXA2) is reported to potentiate vagal nerve neuro-effector transmission in airway smooth muscle tissue. We investigated the effects of BAY u3405 (3(R)-[[4-fluorophenyl)sulfonyl]amino]-1,2,3,4,-tetrahydro-9H-carbazole - 9-propanoic acid), a potent and selective TXA2 receptor antagonist, on the increase in vagal nerve neuro-effector transmission induced by a TXA2 mimetic, U-46619, in the canine trachea. We measured the contractions of canine tracheal smooth muscle evoked by electrical field stimulation (EFS) and by acetylcholine (ACh) in the presence and absence of a subthreshold dose of U-46619 (the highest dose that did not induce any smooth muscle contraction). We then examined whether BAY u3405 inhibited the effect of U-46619 on tracheal smooth muscle. The following results were obtained: (i) subthreshold doses of U-46619 (10(-10) M and 10(-9) M) significantly increased the amplitude of the contractions evoked by EFS; (ii) by contrast, U-46619 had no effect on the contractile response of smooth muscle to exogenously applied ACh; (iii) the contraction evoked by EFS was completely abolished by the application of atropine (10(-6) M) or tetrodotoxin (10(-7) M), indicating that EFS caused the smooth muscle contraction through the release of ACh from vagal nerve terminals; and (iv) pretreatment with BAY u3405 (10(-6) M) abolished the excitatory action of U-46619 on the amplitude of twitch contraction evoked by EFS in the trachea. These results indicate that U-46619, at low concentrations, has a prejunctional action stimulating neuro-effector transmission, presumably increasing ACh release from vagal nerve terminals through TXA2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Animals; Atropine; Carbazoles; Dogs; Electric Stimulation; Female; Male; Muscle Contraction; Muscle, Smooth; Prostaglandin Endoperoxides, Synthetic; Receptors, Thromboxane; Sulfonamides; Synaptic Transmission; Tetrodotoxin; Thromboxane A2; Trachea; Vagus Nerve; Vasoconstrictor Agents

Our previous study in activity sensitized guinea pigs demonstrated an LAR-like increase in respiratory resistance (Rrs) at 3 to 9 hr after PAF inhalation. The result suggested possible involvement of the priming effect of active sensitization and PAF. Mean while, thromboxane A2 (TXA2) is known to be induced by PAF. The present study investigated the involvement of TXA2 in the guinea pig LAR model with a new TXA2 receptor antagonist, BAY u3405. One hr after BAY u3405 administration to guinea pigs sensitized by ovalbumin, the Rrs following inhalation of PAF was subsequently determined. Infiltration of inflammatory cells in the airway tissue 9 hr after PAF inhalation was also observed. While a re-increase in Rrs was found in all the cases in the control group, the re-increase in Rrs was inhibited significantly in the BAY u3405 administration group, 4 to 9 hr after PAF inhalation. The numbers of eosinophils and lymphocytes in the airway tissue were significantly decreased in the BAY u3405 administration group, as compared with the control group. From these results, the possibility is suggested that TXA2 and its direct effect on the airway and the migration-enhancing effect on eosinophils and T lymphocytes, as well as PFA, are involved in the development of LAR by PAF.

Topics: Airway Resistance; Animals; Carbazoles; Guinea Pigs; Male; Platelet Activating Factor; Platelet Aggregation Inhibitors; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Vaccination

The effect of a novel thromboxane A2 receptor antagonist, BAY-u-3405, on experimental allergic airway and skin reactions was studied in vivo. At doses of 3-30 mg/kg BAY-u-3405 clearly inhibited the U-46619-induced increase in respiratory resistance (Rrs) in guinea pigs. BAY-u-3405 at doses of 3 and 30 mg/kg inhibited the aerosolized antigen-induced biphasic increase in respiratory resistance in guinea pigs. Moreover, BAY-u-3405 inhibited repeated aeroantigen-induced airway hyperactivity and airway inflammation in mice. In IgE antibody-mediated biphasic skin reactions in mice, both immediate and late-phase reactions were inhibited by 10 mg/kg of BAY-u-3405. These results demonstrate the efficacy of BAY-u-3405 on the antigen-induced late-phase reactions in the airway and skin in guinea pigs and mice, and antigen-induced airway hyperactivity in mice.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Bronchial Hyperreactivity; Carbazoles; Dermatitis; Guinea Pigs; Hypersensitivity; Immunoglobulin E; Male; Mice; Mice, Inbred BALB C; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

The cardiopulmonary response elicited by intravenous bacteria or endotoxin is well characterized in swine and has two major components. The first represents the acute pulmonary and broncho-constrictive phase (0-2 h) and the second phase (3-8 h) represents increased microvascular permeability, hypotension, and enhanced leukocyte-endothelial adhesion. The pulmonary vasoconstriction and bronchoconstriction of phase 1 results in acute pulmonary hypertension and airway dysfunction, which may result in rapid mortality. Because this acute pulmonary response may not mimic the development of human septic shock, we sought to block this early phase and examine the role of tumor necrosis factor in the latter septic phase (3-8 h). Employing a thromboxane A2 (TXA2) receptor antagonist (BAY U 3405) in the presence of LD100 Escherichia coli challenge, we blocked the acute pulmonary hypertensive phase and prevented early mortality, however, TXA2 blockade did not affect the latter development of septic shock and death. This latter lethal phase, characterized by prolonged leukopenia, was blocked in a dose-dependent manner by tumor necrosis factor monoclonal antibody. We conclude that the TXA2-blocked E. coli-challenged swine may provide a novel animal model in which to investigate the pathophysiology of acute septic shock.

Topics: Animals; Antibodies, Monoclonal; Bronchoconstriction; Capillary Permeability; Carbazoles; Disease Models, Animal; Dose-Response Relationship, Drug; Escherichia coli; Inflammation; Leukocytes; Leukopenia; Lung; Platelet Aggregation Inhibitors; Pulmonary Circulation; Receptors, Thromboxane; Shock, Septic; Sulfonamides; Swine; Thromboxane A2; Tumor Necrosis Factor-alpha; Vasoconstriction

Splanchnic artery occlusion shock was induced in male anaesthetized rats by clamping the splanchnic artery for 45 min. The arteries were then released and survival rate, mean survival time, mean arterial blood pressure, plasma levels of thromboxane B2 and 6-keto-PGF1 alpha, macrophage phagocytosis activity and plasma levels of myocardial depressant factor were evaluated. In addition, the neutrophilic infiltrate was quantified in the ileum and lung using a myeloperoxidase (MPO) assay. Sham splanchnic-artery-occlusion-shocked rats were used as controls. Splanchnic-artery-occlusion-shocked rats died within 93 +/- 7 min, while all sham-shocked animals survived more than 3 h. Splanchnic artery occlusion shock caused changes in mean arterial blood pressure, significantly increased the plasma levels of thromboxane B2 (7.5 +/- 1.3 ng/ml; p < 0.001 vs. sham), 6-keto-PGF1 alpha (8.9 +/- 1.7 ng/ml; p < 0.001 vs. sham) and myocardial depressant factor (114 +/- 11 U/ml), and reduced macrophage phagocytosis. Furthermore, MPO activity was significantly elevated (0.12 +/- 0.03 x 10(-3) and 1.8 +/- 0.5 x 10(-3) U/g protein in the ileum and lung, respectively) 70 min after starting reperfusion. Administration of BAY u3405, a novel thromboxane A2 receptor antagonist (30 mg/kg i.v., 30 min before occlusion), significantly increased survival time (187 +/- 3.7 min) and survival rate, improved mean arterial blood pressure, reduced the plasma levels of myocardial depressant factor (54 +/- 3 U/ml), partially restored macrophage phagocytosis and lowered MPO activity in both the ileum and the lung. Our data are consistent with an involvement of thromboxane A2 in splanchnic artery occlusion shock and suggest that BAY u3405 might be of benefit in low-flow states such as circulatory shock.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Arterial Occlusive Diseases; Blood Pressure; Carbazoles; Macrophages; Male; Myocardial Depressant Factor; Peroxidase; Phagocytosis; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Shock; Splanchnic Circulation; Sulfonamides; Survival Rate; Thromboxane A2; Thromboxane B2

The reduction of blood flow occurring after global cerebral ischemia, designated as delayed postischemic hypoperfusion, is a consequence of various pathological processes. Employing a cardiac arrest model in cats, we evaluated the possible role of thromboxane A2 (TXA2) in reducing the cerebral blood flow (CBF) after transient global ischemia. Twenty cats were divided into two groups, a cardiac arrest group (N = 13) and a sham operation group (N = 7). Following thoracotomy, cardiac arrest was induced for 30 seconds. The TXA2 receptor antagonist, BAY u3405, was injected at 60 minutes after recirculation. The CBF, brain tissue PO2 (BrPO2), brain tissue pH (BrpH) and mean arterial blood pressure (MABP) were measured continuously. The CBF decreased to 89.6% at 60 minutes after the arrest, suggesting postischemic hypoperfusion. Injection of BAY u3405 significantly increased the CBF and BrPO2, whereas BrpH and MABP remained unchanged. In the sham operation group, the CBF, BrPO2, BrpH and MABP did not change significantly during 10 minutes after drug injection, although the BrPO2 was increased mildly at 10 minutes after the injection. Since the thromboxane A2 antagonist improved the CBF only after the cardiac arrest, thromboxane A2 is thought to be one of the factors causing postischemic hypoperfusion.

Topics: Animals; Carbazoles; Cats; Cerebrovascular Circulation; Ischemic Attack, Transient; Perfusion; Reaction Time; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

We investigated the effect of BAY u3405, a thromboxane A2 receptor antagonist in pentobarbital anaesthetized rats subjected to left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham operated rats were used as controls (Sham MI/R). Survival rate, myocardial necrosis, myocardial myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation) and serum creatine phosphokinase activity were studied. Ischaemia-reperfusion injury significantly reduced the survival rate (45%), caused a marked myocardial necrosis, increased serum creatine phosphokinase activity (Sham MI/R = 26 +/- 10.2 U/ml; MI/R = 213 +/- 19 U/ml) and produced a rise in myocardial myeloperoxidase activity in the area-at-risk and in the necrotic area (6.1 +/- 0.4 U x 10(-3)/g tissue and 6.7 +/- 0.9 U x 10(-3)/g of tissue, respectively). The administration of BAY u3405 (30 and 60 mg/kg/i.v., 30 min before occlusion) significantly increased survival rate, lowered the area of myocardial necrosis, blunted the increase in serum creatine phosphokinase activity and reduced the increase in myeloperoxidase activity in both the area-at-risk and the necrotic area. Furthermore, the protective effect of BAY u3405 was dose-dependent. These data are consistent with an involvement of TXA2 in myocardial ischaemia-reperfusion injury and suggest that BAY u3405 may represent a novel therapeutic approach to the treatment of acute ischaemia-reperfusion injury.

Topics: Animals; Carbazoles; Creatine Kinase; Hemodynamics; Leukocytes; Male; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Peroxidase; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

The effect of the specific thromboxane (Tx)A2 receptor antagonist, BAY u 3405 on the late asthmatic response (LAR) was investigated in guinea pigs which are sensitized actively with Ascaris suum antigen. Respiratory resistance (Rrs) of awake guinea pigs was measured by 30 Hz oscillation method for 6 hours after antigen challenge. %Rrs was calculated as the increase rate of Rrs to baseline Rrs (pre-challenge value). Ten mg/kg of BAY u 3405 or vehicle (0.5% methyl cellulose) was administered orally after the end of immediate asthmatic response, i.e., 2 hours after antigen challenge. %Rrs of the control group at 4 and 5 hours after antigen challenge were 101.4 +/- 27.5% and 77.5 +/- 19.9%, respectively. Those of the BAY group were 32.5 +/- 6.2% and 23.5 +/- 5.0%, respectively. %Rrs of the BAY group were significantly lower than those of the control group at both timings (p < 0.05). No significant difference was shown between the BAY group and the control group in the results of the bronchoalveolar lavage (BAL) 4 hours after challenge. Concerning the results of BAL at 6 hours after challenge, the total cell count and its segment, eosinophils count and lymphocytes count in the BAY group were 274.9 +/- 70.5, 62.5 +/- 13.1, 11.3 +/- 3.3 (x 10(5) cells), respectively, resulting in significantly smaller numbers (each p < 0.05) than those in the control group which were 491.9 +/- 55.1, 198.6 +/- 43.9, 32.1 +/- 7.3 (x 10(5) cells), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Airway Resistance; Animals; Asthma; Bronchoalveolar Lavage Fluid; Carbazoles; Guinea Pigs; Leukocyte Count; Lung; Male; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

The two objectives of this study were to assess the potential of BAY U 3405 to prevent arterial thrombosis in response to vessel wall injury and to determine the ability of BAY U 3405 to prevent thrombotic reocclusion after thrombolysis with anisoylated plasminogen streptokinase activator complex.. Dogs were instrumented with a carotid flow probe, stimulating electrode, and a stenosis. Current (150 microA) was applied to the intimal surface of the right carotid artery, and time to occlusive thrombus formation was noted. BAY U 3405 was administered, and the procedure for thrombus formation was repeated for the left carotid artery.. BAY U 3405 administration prevented occlusive arterial thrombosis formation. Ex vivo platelet aggregation was inhibited, bleeding time increased, and thrombus weight reduced after BAY U 3405 treatment. In a second group, thrombi were formed initially in both carotid arteries, BAY U 3405 was administered as before, and anisoylated plasminogen streptokinase activator complex was infused in the right carotid artery proximal to the occlusive thrombus. BAY U 3405 did not alter the incidence of rethrombosis compared with the lytic agent alone.. BAY U 3405 prevented primary arterial thrombosis, corresponding to inhibition of platelet aggregation, and increased bleeding times. BAY U 3405, however, did not prevent rethrombosis after successful thrombolysis with anisoylated plasminogen streptokinase activator complex, despite the fact that platelet reactivity was inhibited. The data are consistent with the concept that the residual thrombus represents a more effective thrombogenic stimulus as compared with arterial wall injury alone and that the mechanisms associated with primary versus secondary thrombus formation may require separate therapeutic approaches.

Topics: Animals; Carbazoles; Carotid Artery Thrombosis; Disease Models, Animal; Dogs; Male; Platelet Aggregation; Platelet Aggregation Inhibitors; Sulfonamides; Thromboxane A2

[3H]-BAY U 3405 was used to characterize the pH-dependency of the binding of various ligands to the TXA2/PGH2-receptor of human platelet membranes. Maximum binding of [3H]-BAY U 3405 is achieved at pH 5.8. In inhibition studies the ligands Daltroban, CTA2, and U 46619 also show a higher affinity at pH 5.8 compared to pH 7.4. In contrast, the ligands I-PTA-OH and GR 32191 have a higher affinity at pH 7.4. No difference is seen with SQ 29548. The ligands I-PTA-OH, GR 32191, and SQ 29548 have a second protonable group in common, which is thought to be the reason for the different pH-dependent binding.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Blood Platelets; Carbazoles; Cell Membrane; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Kinetics; Ligands; Phenylacetates; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Prostaglandin H2; Prostaglandins H; Receptors, Prostaglandin; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Thromboxanes; Vasoconstrictor Agents

Human platelet membranes were used to characterize the receptor binding properties of the specific thromboxane receptor antagonist 3H-SQ 29548 and the displacement of 3H-SQ 29548 from its binding site by the new thromboxane receptor antagonist Bay u 3405. The specific binding of 3H-SQ 29548 was saturable with an association rate constant of 1 x 10(-11) mol-1 min-1 and a dissociation rate constant of 0.032 min-1. Nonspecific binding of 3H-SQ 29548 was below 10%. When Scatchard plot analysis was performed on equilibrium saturation binding the kD was 69 nmol/l and the Bmax was calculated as 3.9 pmol/mg membrane protein. 3H-SQ 29548 was dose dependently displaced from its binding site by addition of increasing concentrations of Bay u 3405 yielding an IC50 value of 68 +/- 12 nmol/l, being not significantly different from the IC50 of nonlabelled SQ 29548 (38 +/- 13 nmol/l). The results show that Bay u 3405 is a potent and specific thromboxane receptor antagonist, displacing 3H-SQ 29548 from its binding site on human platelet membranes with IC50 values being not significantly different. These receptor binding properties and the long biological half life reported in vivo make Bay u 3405 a promissing compound for the treatment of human cardiovascular diseases.

Topics: Binding, Competitive; Blood Platelets; Bridged Bicyclo Compounds, Heterocyclic; Carbazoles; Fatty Acids, Unsaturated; Humans; Hydrazines; In Vitro Techniques; Kinetics; Membranes; Receptors, Prostaglandin; Receptors, Thromboxane; Sulfonamides; Thromboxane A2; Thromboxanes

The new thromboxane A2 antagonist [3H]BAY U 3405 was characterized for its binding to washed human platelets and platelet membranes. In washed platelets the specific binding was reversible, selective and stereospecific, but not saturable. The dissociation constant (Kd) was 6 +/- 2.5 nM, the number of specific binding sites 1177 +/- 306 per platelet. Three structurally different thromboxane A2 (TXA2)/prostaglandin H2 (prostaglandin endoperoxide) (PGH2) receptor ligands completely inhibited the specific binding of [3H]BAY U 3405 in a concentration-dependent manner, indicating that the observed high affinity binding site is the TXA2/PGH2 receptor. In platelet membranes, however, specific [3H]BAY U 3405 binding showed saturability in addition to reversibility, selectivity, and stereospecifity. The Kd of the binding was 9.6 +/- 2.3 nM in kinetic studies and 8.7 +/- 3.7 nM in saturation studies, the inhibition constant (Ki) was 10 +/- 1.1 nM in displacement studies. The TXA2/PGH2 receptor agonists U 46619 and CTA2, and the antagonists Daltroban (BM 13505), I-PTA-OH and SQ 29548 all completely inhibited the specific binding of [3H]BAY U 3405 thus defining the observed binding site as the TXA2/PGH2 receptor. In conclusion, the data suggest that the previously reported TXA2 antagonism of BAY U 3405 is mediated by binding to a specific high affinity binding site of human platelets and platelet membranes that represents the TXA2/PGH2 receptor.

Topics: Blood Platelets; Carbazoles; Cell Fractionation; Cell Membrane; Humans; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Prostaglandin H2; Prostaglandins H; Receptors, Prostaglandin; Receptors, Thromboxane; Sulfonamides; Thromboxane A2

1. The novel thromboxane (TX) antagonist, BAY u3405, has been evaluated against bronchoconstriction induced by the TXA2 mimetic U-46619, prostaglandin D2 (PGD2), 5-hydroxytryptamine (5-HT), leukotriene D4 (LTD4) and histamine in the guinea-pig in vivo by use of a modification of the model described by Konzett & Rössler. 2. When given intravenously (i.v.) at 30 or 100 micrograms kg-1, U-46619 caused 80% maximal bronchoconstriction in most animals. In contrast, PGD2 caused a smaller 40%-50% maximal bronchoconstriction at the highest dose tested (300 micrograms kg-1, i.v.). 3. BAY u3405, given intravenously, orally (p.o.) or by aerosol antagonized U-46619-induced bronchoconstriction in a dose-related manner. The approximate ID50 values were 600 micrograms kg-1, i.v., 1.7 mg kg-1 p.o. and 0.1% w/v 20 breaths by aerosol. 4. BAY u3405 had similar inhibitory activities against U-46619-induced bronchoconstriction and hypertension suggesting that it had no preferential activity on the airways. 5. When given intravenously BAY u3405 antagonized the bronchoconstrictor effect of intravenous PGD2 with ID50 values between 30-100 micrograms kg-1. 6. The action of BAY u3405 (10 mg kg-1, p.o.) was long lasting, causing significant inhibition of U-46619-induced bronchoconstriction 7 h after dosing. 7. At 1 mg kg-1, i.v., a dose that abolished the response to U-46619 and PGD2, BAY u3405 had no effect on histamine-, 5-HT- or LTD4-induced bronchoconstriction. 8. BAY u3405 potently and selectively antagonized U-46619- or PGD2-induced bronchoconstriction in the Konzett-Rössler model of guinea-pig lung function. It should therefore prove to be a useful tool for defining the role of TXA2- and PGD2 in airway diseases such as asthma.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Administration, Oral; Aerosols; Animals; Blood Pressure; Bronchoconstriction; Carbazoles; Guinea Pigs; Histamine; In Vitro Techniques; Injections, Intravenous; Male; Prostaglandin D2; Prostaglandin Endoperoxides, Synthetic; Serotonin; SRS-A; Sulfonamides; Thromboxane A2; Thromboxanes

The model of AA-induced sudden death employed in these investigations seems to be appropriate for studying the efficacy of TXA2-antagonists. The actions of TXA2 on platelets, respiratory and vascular tissue are considered as key events resulting in the death of the animals. The results obtained in this study, using BAY U 3405 as a selective TXA2 receptor antagonist, clearly show that TXA2 mediated processes are effectively abolished by this type of drug. Since TXA2 is implicated in the pathophysiology of many diseases, potent TXA2 antagonists appear to be useful for treatment of these disorders. BAY U 3405 seems to fulfil these requirements. The threshold dose is 1 to 3 mg/kg p.o. In addition, there is a rapid onset and long duration of action at 10 mg/kg p.o. under the experimental conditions used.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bronchoconstriction; Carbazoles; Death, Sudden; Dose-Response Relationship, Drug; Male; Platelet Aggregation; Rabbits; Sulfonamides; Survival Rate; Thromboembolism; Thromboxane A2; Thromboxanes

Injection of sodium arachidonate (NaAr) intravenously at a dose of 2 mg/kg is uniformly lethal in rabbits within 3 min. This sudden death is characterized by a precipitous drop in mean blood pressure within 2 min after injection of NaAr, a marked decrease in the circulating platelet count, a significant increase in intratracheal pressure and in plasma thromboxane A2 (TxA2) concentration as measured by radioimmunoassay of its stable breakdown product, TxB2. Pretreatment with Bay-u-3405, a new specific thromboxane receptor antagonist, at a dose of 1 or 10 mg/kg dramatically protected rabbits against sudden death induced by injection of NaAr. All of the rabbits treated with either of these two doses of Bay-u-3405 survived, and their thrombocytopenia, elevated plasma TxB2 concentration and bronchoconstriction were significantly attenuated. However, administration of 0.1 mg/kg Bay-u-3405 exerted no protective effect in this lethal model. Bay-u-3405 was shown to be a potent and specific inhibitor of thromboxane-mimetic induced platelet aggregation in vitro. Our data clearly show that Bay-u-3405 is a very effective protective agent against NaAr-induced sudden death in rabbits, blocking all of the known deleterious effects of TxA2.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Blood Pressure; Bronchi; Carbazoles; Death, Sudden; Electrocardiography; Male; Platelet Aggregation; Platelet Aggregation Inhibitors; Rabbits; Radioimmunoassay; Sulfonamides; Thromboxane A2; Thromboxanes

Platelet activation results in the formation of various vasoactive mediators such as thromboxane A2 and serotonin. We investigated the effects of Bay U 3405 [(3R)-3- (4-fluorophenyl-sulfonamido)-1,2,3,4,-tetrahydro-9-carbazolepro panoic acid] on vasocontractions of isolated bovine cerebral arteries induced by U 46.619, a stable thromboxane/prostaglandin-endoperoxide analogue, and authentic thromboxane A2 released from thrombin-stimulated human platelets. Bay U 3405 (0.001-10 mumol/l) potently inhibited the contraction induced by U 46.619 and demonstrated a reduction of the thromboxane-mediated component of platelet-induced contractile response at higher concentrations (0.1-10 mumol).

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Blood Platelets; Carbazoles; Cattle; Cerebral Arteries; Humans; Ischemic Attack, Transient; Prostaglandin Endoperoxides, Synthetic; Serotonin; Sulfonamides; Thromboxane A2; Thromboxanes; Vasoconstriction

The synthesis of (3R)-3-(4-Fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9- carbazolepropanoic acid (Bay u 3405), a new, enantiomerically pure antagonist of thromboxane A2, is described. The determination of the absolute configuration of Bay u 3405 was performed by an X-ray analysis of compound 7 ([3((2S)-acetylamido)-3-phenylpropionamido]-1,2,3,4- tetrahydro-carbazol). Bay u 3405 is in vitro 1 to 2 orders of magnitude more active than its (-)-enantiomer Bay u 3406.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Carbazoles; Chemical Phenomena; Chemistry; Humans; In Vitro Techniques; Molecular Conformation; Muscle Contraction; Muscle, Smooth, Vascular; Platelet Aggregation; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Rabbits; Stereoisomerism; Sulfonamides; Thromboxane A2

(3R)-3-(4-Fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9-carbazo lepropanoic acid (Bay u 3405) was tested for inhibition of platelet aggregation in vitro (human platelet rich plasma) and ex vivo (rat). Aggregation induced by collagen, arachidonic acid, thrombin, adenosine diphosphate (ADP, biphasic response), epinephrine and U 46619 was inhibited at minimum effective concentrations of 0.01 to 0.1 micrograms/ml in vitro. Following oral administration to rats the ED50 for the dose-dependent inhibition was 36 micrograms/kg. At a dose of 100 micrograms/kg p.o. significant inhibition was obtained up to 16 h. Bay u 3405 is considered a potential drug for treatment of some cardiovascular disorders.

Topics: Animals; Carbazoles; Collagen; Dose-Response Relationship, Drug; In Vitro Techniques; Male; Platelet Aggregation; Platelet Aggregation Inhibitors; Rats; Rats, Inbred Strains; Sulfonamides; Thromboxane A2

The effects of thromboxane (Tx)A2 antagonism were examined in a canine model of platelet-dependent coronary occlusion. The novel TxA2 antagonist (3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9-carbazo lepropanoic acid (Bay u 3405) was studied to ensure that antithrombotic effects seen in vivo were platelet-mediated and did not reflect unspecific compound effects. Bay u 3405 (1, 3, 10 and 30 mg/kg i.v.) inhibited in vivo platelet aggregation and increased the time to thrombotic vascular occlusion by 2.8 h (p less than 0.05) after 30 mg/kg were given. A dose-dependent reduction of intravascular occlusive thrombus growth occurred: thrombus wet weight decreased from 66 +/- 6 mg in vehicle controls to 42 +/- 6 mg, 25 +/- 5 mg, 18 +/- 3 mg and 6 +/- 2 mg after administration of 1, 3, 10 and 30 mg Bay u 3405 i.v., respectively. Electrocardiographic signs for developing myocardial ischemia were largely prevented by the compound. Collagen-induced platelet aggregation ex vivo was inhibited by over 60% in drug-treated animals. The observed delay of thrombotic coronary occlusion reflected an inhibition of platelet aggregation and protection from coronary vasoconstriction at the site of thrombus formation, most likely mediated through blockade of TxA2 receptors.

Topics: Animals; Blood Pressure; Carbazoles; Coronary Circulation; Coronary Disease; Coronary Thrombosis; Dogs; Electric Stimulation; Female; Fibrinolytic Agents; Heart Rate; Humans; In Vitro Techniques; Male; Myocardial Infarction; Sulfonamides; Thromboxane A2