sq-29548 and furegrelate

Lung cancer concerns a worldwide health problem and the efficacy of available treatments is unsatisfactory. Recently, thromboxane A2 (TXA2) synthase (TXAS) and receptor (TXA2R) have been documented to play a role in lung cancer development. Therefore, dual TXA2R modulator (i.e., the dual blocker of TXAS and TXA2R) may be more efficacious to kill lung tumor cells than single TXAS inhibitor or TXA2R antagonism. The close relationship between cyclooxygenase (COX)-2 and TXAS also raises whether or how TXA2 contributes to the oncogenic activity of COX-2. This study is therefore conducted to answer these questions.. Various inhibitors and siRNA were used to evaluate the roles of TXA2 and COX-2 in the proliferation and apoptosis of lung adenocarcinoma cells. Cell proliferation was detected using both MTS ELISA and BrdU labeling ELISA. Cell cycle distribution and apoptosis were examined by flow cytometric analysis. TXB2 level, reflecting the biosynthesis of TXA2, was detected by peroxidase-labeled TXB2 conjugates using an enzyme immunoassay kit. Western blotting was performed to evaluate many biomarkers for cell cycles, apoptosis and proliferation. The levels of COXs were screened by reverse transcriptase and real-time quantitative PCR.. We found either single TXAS inhibitor/TXA2R antagonist or the dual TXA2 modulators offered a similar inhibition on cell proliferation. Moreover, inhibition of TXA2 arrested cells at the G2/M phase and induced apoptosis. It is further demonstrated that TXA2 was able to function as a critical mediator for tumor-promoting effects of COX-2 in lung adenocarcinoma cells.. The present study has for the first shown that dual TXA2 modulators and the single blocker of TXAS or TXA2R offer a similar inhibitory role in lung adenocarcinoma cell proliferation and that the tumor-promoting effects of COX-2 can largely be relayed by TXA2. Thus, TXA2 should be regarded as a critical molecule in COX-2-mediated tumor growth and a valuable target against lung cancer.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenocarcinoma; Adenocarcinoma of Lung; Antineoplastic Agents; Apoptosis; Benzofurans; Blotting, Western; Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cyclooxygenase 2; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Fatty Acids, Unsaturated; Flow Cytometry; Humans; Hydrazines; Immunoenzyme Techniques; Lung Neoplasms; Nitrobenzenes; Real-Time Polymerase Chain Reaction; Receptors, Thromboxane; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Sulfonamides; Sulfonylurea Compounds; Thromboxane A2; Thromboxane-A Synthase

The aim of the current study was to determine the central cyclooxygenase (COX) pathway and central thromboxane signaling in the cardiovascular effects evoked by arachidonic acid (AA). As a main control for the study, different doses of AA (75, 150, or 300 µg) were administered intracerebroventricularly (i.c.v.). Centrally injected AA dose- and time-dependently increased mean arterial pressure and decreased heart rate in conscious normotensive Sprague-Dawley rats. The maximal cardiovascular effects of AA were observed at min 10 of the injection and lasted almost 30 min. To investigate the central mechanism of the AA-induced cardiovascular effect in conscious normotensive animals, pretreatment with nonselective COX inhibitor indomethacin (200 µg; i.c.v.), thromboxane A2 (TXA2) synthesis inhibitor furegrelate (250 or 500 µg; i.c.v.), or TXA2 receptor antagonist SQ-29548 (8 or 16 µg; i.c.v.) was carried out 15 min before AA (150 µg; i.c.v.) injection. While indomethacin completely prevented the pressor and bradycardic responses to AA, furegrelate and SQ-29548 attenuated these effects in part in awake normotensive rats. In conclusion, these findings suggest that the pressor and bradycardic cardiovascular effects of centrally injected AA are dependent on COX activity being totally central and the TXA2 signaling pathway being subsequently central, at least in part.

Topics: Animals; Arachidonic Acid; Benzofurans; Blood Pressure; Bradycardia; Bridged Bicyclo Compounds, Heterocyclic; Cardiovascular System; Fatty Acids, Unsaturated; Heart Rate; Hydrazines; Indomethacin; Infusions, Intraventricular; Male; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane A2, Prostaglandin H2; Signal Transduction; Thromboxane A2

The role of enzymes and receptors of the prostanoid pathway in the inhibitory effect of 8-isoprostaglandin E2 (8-isoPGE2) on endogenous amino acid neurotransmitter levels was examined, ex vivo. Freshly isolated bovine eyeballs were injected intravitreally with IsoPs, incubated in Krebs buffer for 30 min and retina prepared for HPLC-ECD detection of amino acids. 8-isoPGE2 attenuated retinal glutamate and its metabolite, glutamine and glycine in a concentration-dependent manner. The nonselective cyclooxygenase (COX)-inhibitor, flurbiprofen, COX-2 selective inhibitor, NS-398 and thromboxane (Tx) synthase inhibitor, furegrelate had no effect on both basal amino acid levels and the inhibitory effects of 8-isoPGE2 (1-100 μM) on the retinal amino acids. Whereas the TP-receptor antagonist SQ-29548(10 μM) exhibited no effect, SC-19220(EP1; 30 μM), AH-6809(EP(1-3); 30 μM) and AH-23848(EP4; 30 μM) reversed the inhibitory effects of 8-isoPGE2 (0.01-100 μM) on glutamate, glutamine and glycine levels. We conclude that prostanoid EP-receptors regulate the inhibitory effect of 8-isoPGE2 on basal levels of endogenous amino acids in bovine retina, ex vivo.

Topics: Animals; Benzofurans; Biphenyl Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cattle; Cyclooxygenase Inhibitors; Dibenz(b,f)(1,4)oxazepine-10(11H)-carboxylic acid, 8-chloro-, 2-acetylhydrazide; Dinoprostone; Fatty Acids, Unsaturated; Flurbiprofen; Glutamic Acid; Glutamine; Glycine; Hydrazines; Isoprostanes; Neurotransmitter Agents; Nitrobenzenes; Prostaglandins; Receptors, Prostaglandin; Retina; Sulfonamides; Xanthones

This study examines the effect of ovarian function on thromboxane A(2) (TXA(2)), prostaglandin (PG) I(2), PGF(2alpha), and PGE(2) release as well as the role of these substances in nitric oxide (NO) release and acetylcholine (ACh)-mediated relaxation.. Aortic segments from ovariectomized and control female Sprague-Dawley rats were used. Cyclooxygenase (COX-1 and COX-2) expression was studied. ACh-induced relaxation was analysed in the absence and presence of the COX-2 inhibitor NS-398, the TXA(2) synthesis inhibitor furegrelate, the PGI(2) synthesis inhibitor tranylcypromine (TCP), or the thromboxane-prostanoid receptor antagonist SQ-29548. TXA(2), PGI(2), PGF(2alpha), and PGE(2) release was measured, and the vasomotor effect of exogenous TXA(2), PGI(2,) PGF(2alpha), and PGE(2) was assessed. Basal and ACh-induced NO release in the absence and presence of NS-398, furegrelate, TCP, or TCP plus furegrelate was studied. Ovariectomy did not alter or increased COX-1 or COX-2 expression, respectively. NS-398 decreased, and furegrelate did not change, the ACh-induced relaxation in arteries from both groups. SQ29,548 decreased the ACh-induced relaxation only in aortas from ovariectomized rats. TCP decreased the ACh-induced relaxation in both groups, and furegrelate or SQ29,548 totally restored that response only in aortas from control rats. Ovariectomy increased the ACh-induced TXA(2), PGI(2), and PGE(2) release and the contractile responses induced by exogenous TXA(2), PGF(2alpha), or PGE(2), while it decreased the PGI(2)-induced vasodilator response. In aortas from control rats, NS-398 did not alter the ACh-induced NO release, and furegrelate, TCP, or TCP plus furegrelate increased that release. In arteries from ovariectomized rats, NS-398, furegrelate, TCP, or TCP plus furegrelate decreased the ACh-induced NO release.. Despite the prevalence of vasoconstrictor prostanoids derived from COX-2 in aortas from ovariectomized rats, the ACh-induced relaxation is maintained, probably as consequence of the positive regulation that prostanoids exert on eNOS activity.

Topics: Acetylcholine; Animals; Aorta; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Dinoprost; Dinoprostone; Dose-Response Relationship, Drug; Epoprostenol; Fatty Acids, Unsaturated; Female; Hydrazines; Intramolecular Oxidoreductases; Membrane Proteins; Nitric Oxide; Nitrobenzenes; Ovariectomy; Prostaglandins; Rats; Rats, Sprague-Dawley; Receptors, Prostaglandin; Sulfonamides; Thromboxane A2; Thromboxane-A Synthase; Tranylcypromine; Vasodilation; Vasodilator Agents

We reported that the endothelial dysfunction that develops with age was associated with a proinflammatory phenotype. In this study, we hypothesized that an increased production of proinflammatory cyclooxygenase (COX) products occurs before endothelial dysfunction. Dilations to acetylcholine (ACh) were recorded from pressurized renal arteries isolated from 3- and 6-mo-old C57Bl/6 male mice treated or not with the polyphenol catechin (30 mg x kg(-1) x day(-1)) in drinking water for 3 mo. Release of thromboxane (TX) B(2), the metabolite of TXA(2), was measured by using immunoenzymatic assays, and free radical production was measured by using the fluorescent dye CM-H(2)DCFDA. Endothelial nitric oxide synthase (eNOS) and COX-1/2 mRNA expression were quantified by quantitative PCR. N(G)-nitro-L-arginine (L-NNA) reduced (P < 0.05) ACh-induced dilation in vessels isolated from 3- and 6-mo-old mice. In the presence of L-NNA, indomethacin normalized (P < 0.05) the dilation in vessels from 6-mo-old mice only. SQ-29548 (PGH(2)/TXA(2) receptor antagonist) and furegrelate (TXA(2) synthase inhibitor), in the presence of L-NNA, also improved (P < 0.05) dilation. L-NNA increased TXA(2) release and free radical-associated fluorescence, the latter being prevented by SQ-29548. In vessels from 6-mo-old mice treated with catechin for 3 mo, L-NNA-dependent reduction in ACh-mediated dilation was insensitive to indomethacin, whereas TXA(2) release and free radical-associated fluorescence were prevented. eNOS mRNA expression was significantly increased by catechin treatment. Our results suggest that an augmented production of TXA(2) and the associated change in redox regulation precede the development of the endothelial dysfunction.

Topics: Acetylcholine; Acetylcysteine; Aging; Animals; Antioxidants; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Catechin; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Fatty Acids, Unsaturated; Gene Expression Regulation, Enzymologic; Hydrazines; Indomethacin; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Nitric Oxide; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Oxidation-Reduction; Reactive Oxygen Species; Receptors, Thromboxane A2, Prostaglandin H2; Renal Artery; RNA, Messenger; Thromboxane A2; Thromboxane B2; Thromboxane-A Synthase; Vasodilator Agents

The current study was designed to determine the cardiovascular effect of centrally administrated melittin, a phospholipase A2 (PLA2) activator, and the mediation of central thromboxane A2 (TXA2) and its receptors in normotensive conscious rats. Studies were performed in normotensive male Sprague Dawley rats injected intracerebroventricularly (i.c.v.) with melittin. Melittin (1.5, 3.0, 6.0 microg/5.0 microl; i.c.v.) caused dose- and time-dependent increases in mean arterial pressure (MAP) and decrease in heart rate (HR). Maximal effects were observed 5-10 min after 3.0 microg dose of melittin. In order to test the mediation of central TXA2 and its central receptors in the cardiovascular effect of melittin, the rats were pretreated with furegrelate (500.0 microg; i.c.v.), a TXA2 synthesis inhibitor, and SQ-29548 (8.0 microg; i.c.v.), a TXA2 receptor antagonist, 15 min prior to melittin (3.0 microg). Furegrelate or SQ-29548 partially inhibited the pressor effect and bradycardia elicited by melittin. In conclusion, our findings show that centrally administered melittin increases MAP and decreases HR in conscious rats. Moreover, according to our findings, central TXA2 and its receptors may in part mediate melittin-induced cardiovascular effects.

Topics: Animals; Benzofurans; Blood Pressure; Bridged Bicyclo Compounds, Heterocyclic; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Inhibitors; Fatty Acids, Unsaturated; Heart Rate; Hydrazines; Male; Melitten; Phospholipases A; Phospholipases A2; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane A2, Prostaglandin H2; Thromboxane A2

We examined the role of thromboxane A2 (TXA2) in LPS-induced hyperresponsiveness of hepatic portal circulation to endothelins (ETs) and whether Kupffer cells are the primary source of TXA2 release in response to ET-1 in endotoxemia. After 6 h of LPS (1 mg/kg body wt ip) or saline (control), liver was isolated and perfused with recirculating Krebs-Henseleit bicarbonate buffer at a constant flow rate (100 ml.min(-1).kg body wt(-1)). ET-1 (10 pmol/min) was infused for 10 min. Portal pressure (PP) was continuously monitored during perfusion. Perfusate was sampled for enzyme immunoassay of thromboxane B2 (TXB2; the stable metabolite of TXA2) and lactate dehydrogenase (LDH) assay. ET-1 infusion resulted in a significantly greater increase of PP in the LPS group than in controls. Both TXA2 synthase inhibitor furegrelate (Fureg) and TXA2 receptor antagonist SQ-29548 (SQ) substantially blocked enhanced increase of PP in the LPS group (4.9 +/- 0.4 vs. 3.6 +/- 0.5 vs. 2.6 +/- 0.6 mmHg for LPS alone, LPS + Fureg, and LPS + SQ, respectively; P < 0.05) while having no significant effect on controls. GdCl3 for inhibition of Kupffer cells had similar effects (4.9 +/- 0.4 mmHg vs. 2.9 +/- 0.4 mmHg for LPS alone and GdCl3 + LPS, respectively; P < 0.05). In addition, the attenuated PP after ET-1 was found concomitantly with significantly decreased releases of TXB2 and LDH in LPS rats treated with Fureg, SQ, and GdCl3 (886.6 +/- 73.4 vs. 110.8 +/- 0.8 vs. 114.8 +/- 54.7 vs. 135.2 +/- 45.2 pg/ml, respectively; P < 0.05). After 6 h of LPS, Kupffer cells in isolated cell preparations released a significant amount of TXA2 in response to ET-1. These results clearly indicate that hyperresponsiveness of hepatic portal circulation to ET-1 in endotoxemia is mediated at least in part by TXA2-induced receptor activation, and Kupffer cells are likely the primary source of increased TXA2 release.

Topics: Animals; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Endothelin-1; Endotoxemia; Fatty Acids, Unsaturated; Gadolinium; Hydrazines; Kupffer Cells; Lipopolysaccharides; Liver; Male; Portal Pressure; Portal System; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Thromboxane A2; Thromboxane-A Synthase

We previously showed that testosterone, administered in vivo, increases the tone of cerebral arteries. A possible underlying mechanism is increased vasoconstriction through the thromboxane A2 (TxA2) pathway. Therefore, we investigated the effect of chronic testosterone treatment (4 wk) on TxA2 synthase levels and the contribution of TxA2 to vascular tone in rat middle cerebral arteries (MCAs). Using immunofluorescence and confocal microscopy, we demonstrated that TxA2 synthase is present in MCA segments in both smooth muscle and endothelial layers. Using Western blot analysis, we found that TxA2 synthase protein levels are higher in cerebral vessel homogenates from testosterone-treated orchiectomized (ORX + T) rats compared with orchiectomized (ORX) control animals. Functional consequences of changes in cerebrovascular TxA2 synthase were determined using cannulated, pressurized MCA segments in vitro. Constrictor responses to the TxA2 mimetic U-46619 were not different between the ORX + T and ORX groups. However, dilator responses to either the selective TxA2 synthase inhibitor furegrelate or the TxA2-endoperoxide receptor (TP) antagonist SQ-29548 were greater in the ORX + T compared with ORX group. In endothelium-denuded arteries, the dilation to furegrelate was attenuated in both the ORX and ORX + T groups, and the difference between the groups was abolished. These data suggest that chronic testosterone treatment enhances TxA2-mediated tone in rat cerebral arteries by increasing endothelial TxA2 synthesis without altering the TP receptors mediating constriction. The effect of in vivo testosterone on cerebrovascular TxA2 synthase, observed here after chronic hormone administration, may contribute to the risk of vasospasm and thrombosis related to cerebrovascular disease.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Androgens; Animals; Benzofurans; Body Weight; Bridged Bicyclo Compounds, Heterocyclic; Enzyme Inhibitors; Fatty Acids, Unsaturated; Hydrazines; Male; Middle Cerebral Artery; Orchiectomy; Rats; Rats, Inbred F344; Receptors, Thromboxane; Testosterone; Thromboxane A2; Thromboxane-A Synthase; Vasoconstriction; Vasoconstrictor Agents; Vasodilation

Blood pressure (BP) is typically higher in men than in women. As in humans, BP is higher in male spontaneously hypertensive rats (SHRs) than in female SHRs. The mechanism(s) responsible for the higher BP in men and male rats has not been elucidated.. The present study tested the hypothesis that thromboxane and/or the thromboxane A(2)/prostaglandin H(2) receptor (TxR) plays a role in the gender difference in BP in SHRs.. Male and female SHRs were treated with the TxR antagonist SQ29548 (2 microg/kg/min into the jugular vein) via minipump for 2 weeks; mean arterial pressure (MAP) and renal hemodynamic function were measured. To determine whether thromboxane played a role in the higher MAP in SHRs, male and female rats were treated with the thromboxane synthase inhibitor (TxI) furegrelate, 30 mug/kg/min, via minipump, for 2 weeks.. MAP was reduced with TxR antagonism in male but not in female SHRs. In addition, TxR antagonism in males caused renal vasodilation with increases in glomerular filtration rate and renal plasma flow, and reductions in renal vascular resistance. In contrast, MAP was not affected by the TxI in either males or females.. These data support a role for TxR, but not thromboxane, in mediating the gender difference in BP in SHRs.

Topics: Analysis of Variance; Animals; Benzofurans; Blood Pressure; Bridged Bicyclo Compounds, Heterocyclic; Fatty Acids, Unsaturated; Female; Hemodynamics; Hydrazines; Male; Rats; Rats, Inbred SHR; Sex Factors; Thromboxane-A Synthase

We tested the hypothesis that thromboxane generation mediates vasoconstriction of isolated outer medullary descending vasa recta (OMDVR) by angiotensin (Ang) II. The lipoxygenase and cyclooxygenase (COX) inhibitor eicosatetraynoic acid (1 micromol/L) and the COX inhibitor indomethacin (1 micromol/L) partially reversed Ang II (1 nmol/L) constriction of in vitro perfused OMDVR. To determine whether thromboxane is a mediator of Ang II-induced vasoconstriction, a thromboxane synthase inhibitor, U63577A (1 micromol/L), and thromboxane receptor antagonists, SQ-29548 or BMS-180,291 (1 micromol/L, each), were introduced into the bath of vessels that had been preconstricted by Ang II (1 nmol/L). These agents significantly inhibited vasoconstriction induced by Ang II. In contrast, SQ-29548 and U63557A did not affect vessels preconstricted by raising extracellular KCl from 5 to 100 mmol/L. The thromboxane receptor agonist U46619 (1 micromol/L) constricted OMDVR, an effect that was blocked by the antagonist BMS-180,291. In separate protocols, microperfused OMDVR were pretreated with U63577A or SQ-29548, after which they were exposed to luminal Ang II to induce vasoconstriction. Both agents inhibited vasoconstriction whether preexposure to them was via the bath or the perfusate. We conclude that Ang II-induced constriction of OMDVR is partly mediated by metabolites of arachidonic acid, including thromboxanes.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 5,8,11,14-Eicosatetraynoic Acid; Angiotensin II; Animals; Benzofurans; Blood Vessels; Bridged Bicyclo Compounds, Heterocyclic; Culture Techniques; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Fatty Acids, Unsaturated; Female; Hydrazines; Indomethacin; Kidney Medulla; Kinetics; Lipoxygenase Inhibitors; Potassium Chloride; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Thromboxane-A Synthase; Thromboxanes; Vasoconstriction; Vasoconstrictor Agents

Prostaglandin endoperoxide H synthases and their arachidonate products have been implicated in modulating angiogenesis during tumor growth and chronic inflammation. Here we report the involvement of thromboxane A(2), a downstream metabolite of prostaglandin H synthase, in angiogenesis. A TXA(2) mimetic, U46619, stimulated endothelial cell migration. Angiogenic basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) increased TXA(2) synthesis in endothelial cells three- to fivefold. Inhibition of TXA(2) synthesis with furegrelate or CI reduced HUVEC migration stimulated by VEGF or bFGF. A TXA(2) receptor antagonist, SQ29,548, inhibited VEGF- or bFGF-stimulated endothelial cell migration. In vivo, CI inhibited bFGF-induced angiogenesis. Finally, development of lung metastasis in C57Bl/6J mice intravenously injected with Lewis lung carcinoma or B16a cells was significantly inhibited by thromboxane synthase inhibitors, CI or furegrelate sodium. Our data demonstrate the involvement of TXA(2) in angiogenesis and development of tumor metastasis.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Chemotaxis; Dinoprost; Dinoprostone; Endothelial Growth Factors; Endothelium, Vascular; Enzyme Inhibitors; Epoprostenol; Fatty Acids, Unsaturated; Fibroblast Growth Factor 2; Humans; Hydrazines; Lung Neoplasms; Lymphokines; Male; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Neoplasm Metastasis; Neovascularization, Pathologic; Rats; Receptors, Thromboxane; Thromboxane A2; Thromboxane-A Synthase; Umbilical Veins; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

The nitric oxide-mediated portion of shear stress-induced dilation of rat gracilis muscle arterioles was shown to be impaired in spontaneously hypertensive rats (SHR). Because shear stress-induced dilation is primarily mediated by endothelium-derived prostaglandins in rat cremasteric arterioles, we hypothesized that in the cremasteric vascular bed the mediation of shear stress-induced dilation by prostaglandins is altered in hypertension. At a constant intraluminal pressure of 80 mm Hg, the active diameters of isolated rat cremasteric arterioles of normotensive 30-week-old Wistar-Kyoto rats (WKY) and SHR were 58.0+/-3.1 and 51.7+/-3.6 microm, respectively, whereas their passive diameters were 109.4+/-4.4 and 101.9+/-6.7 microm, respectively. Dilations to increases in shear stress elicited by increases in intraluminal flow (from 0 to 25 microL/min) were significantly less (P<0.05) in cremasteric arterioles isolated from SHR than from WKY. Arachidonic acid (10(-5) mol/L) elicited constrictions in SHR arterioles but dilations in WKY arterioles. The prostaglandin H(2)/thromboxane A(2) (PGH(2)/TxA(2)) receptor antagonist SQ 29,548 (10(-6) mol/L) significantly increased basal diameter by 11% and normalized the attenuated shear stress-induced dilation in SHR, whereas it did not affect basal diameter and arteriolar responses of WKY. Furegrelate, a specific inhibitor of TxA(2) synthase, did not affect the response in SHR. Also, SQ 29,548 reversed the arachidonic acid-induced constriction to dilation in SHR arterioles, whereas it did not affect the dilator response in WKY arterioles. Constrictions of arterioles of WKY and SHR to U46,619 (a PGH(2)/TxA(2) receptor agonist) were not different. These results demonstrate that in cremasteric arterioles of hypertensive rats, shear stress elicits an enhanced release of PGH(2), resulting in a reduced shear stress-dependent dilation. Thus, augmented hemodynamic forces can alter the shear stress-induced synthesis of prostaglandins, which may contribute to the elevated vascular resistance in hypertension.

Topics: Animals; Arterioles; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Enzyme Inhibitors; Fatty Acids, Unsaturated; Hydrazines; Hypertension; Prostaglandin H2; Prostaglandins H; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Prostaglandin; Receptors, Thromboxane A2, Prostaglandin H2; Stress, Mechanical; Thromboxane-A Synthase

The influence of hydronephrosis (6-10 wk) on the renal vascular response to arginine vasopressin (AVP) was assessed, using isolated perfused normal and hydronephrotic rat kidneys. In normal kidneys, AVP (0.3 nM) reduced renal perfusate flow (RPF) by 55 +/- 7% (P < 0.01). AVP-induced decrements in RPF were reversed partially by diltiazem (10 microM) and completely by 10 nM of an AVP (V1)-receptor antagonist (AVPX). In hydronephrotic kidneys, AVP reduced RPF by 81 +/- 2% (P < 0.01) and constricted afferent (AA) and efferent arterioles (EA) by 33 +/- 3 (P < 0.01) and 33 +/- 5% (P < 0.01), respectively. The addition of diltiazem altered neither RPF nor vessel diameters. Administration of AVPX recovered RPF, AA, and EA diameters. When hydronephrotic kidneys were pretreated with thromboxane (Tx) inhibitors, AVP reduced RPF by 62 +/- 5% (P < 0.01) and constricted AAs and EAs by 26 +/- 2 (P < 0.01) and 17 +/- 3% (P < 0.05), respectively. Under Tx blockade, diltiazem partially reversed the AVP-induced reduction in RPF and restored the decrements in AA diameter. Subsequent addition of AVPX returned RPF and EA diameter. Our data indicate that AVP elicits substantial renal microvascular constriction and suggest that AVP stimulates Tx production in hydronephrotic kidneys, thereby altering renal vascular responsiveness to this peptide.

Topics: Animals; Antidiuretic Hormone Receptor Antagonists; Arginine Vasopressin; Arterioles; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Enzyme Inhibitors; Fatty Acids, Unsaturated; Hydrazines; Hydronephrosis; In Vitro Techniques; Male; Rats; Rats, Sprague-Dawley; Reference Values; Renal Circulation; Thromboxane-A Synthase; Thromboxanes; Vasoconstriction

This study compared the effects of a thromboxane synthase inhibitor, thromboxane receptor antagonist, and cyclooxygenase inhibitor in a canine arterial graft patency model. Fifty-six dogs were divided into a control (no treatment) and five treatment groups: thromboxane synthase inhibitor (U63557A; 15 mg/kg/tid); thromboxane receptor antagonist (SQ29548; 0.02 mg/kg/hr); high-dose aspirin (325 mg/day; low-dose aspirin (1 mg/kd/day; and aspirin plus dipyridamole (325 mg/day aspirin; 3 mg/kg/day dipyridamole). Drugs were orally administered except for thromboxane receptor antagonist, which was delivered intravenously by minosmotic pumps. After 24 hours of drug treatment, bilateral femoral artery prosthetic grafts (4 mm diameter x 7 cm; 1 polytetrafluoroethylene and 1 Dacron) were implanted. Patency was determined after 1 week. Dogs were classified before operation according to their epinephrine-enhanced arachidonate-stimulated platelet aggregation response. Polytetrafluoroethylene and Dacron graft patency rates were equivalent in all groups. Overall graft patency was significantly improved from 42% (control) to 94% by both high-dose aspirin and thromboxane receptor antagonist (p less than 0.001). Aspirin-dipyridamole also improved patency (83%; p less than 0.01 versus control), whereas thromboxane synthase inhibitor and low-dose aspirin were not effective. Baseline platelet aggregation was not predictive of patency. The drugs that promoted graft patency in this model either suppressed both thromboxane A2 and prostaglandin H2 formation (high-dose aspirin) or blocked their combined platelet receptor (thromboxane receptor antagonist). Thromboxane synthase inhibitor may be ineffective because prostaglandin H2 production is allowed. These data suggest that activation of the platelet thromboxane A2-prostaglandin H2 receptor is an essential event in early arterial graft thrombosis.

Topics: Animals; Aspirin; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Dipyridamole; Dogs; Fatty Acids, Unsaturated; Graft Occlusion, Vascular; Hydrazines; Male; Platelet Aggregation; Receptors, Prostaglandin; Receptors, Thromboxane; Thromboxane A2; Thromboxane-A Synthase; Vascular Patency

Since thromboxane A2 (TXA2) release may relate to the extension of myocardial injury following coronary ligation, the authors examined the effects of pretreatment with a selective TXA2 synthetase inhibitor U-63,557A, or a TXA2 receptor antagonist SQ-29,548, on myocardial infarct size forty-eight hours following left coronary ligation in rats. Myocardial infarct size (as percent of left ventricle, LV) was decreased from 44 +/- 3% in saline-treated control animals to 34 +/- 4% (P less than 0.05) in U-63,557A-treated animals and to 32 +/- 4% (P less than 0.05) in SQ-29,548 treated animals (U-63,557A-treated vs SQ-29,548-treated, P = NS). LV creatine kinase (CK) was 5.08 +/- 0.42 IU/mg protein in noninfarcted untreated rats and 1.79 +/- 0.21 IU/mg protein in saline-treated infarcted rats. LV CK was 2.86 +/- 0.40 IU/mg protein in U-63,557A-treated rats and 3.11 +/- 0.51 IU/mg protein in SQ-29,548-treated infarcted rats (both P less than 0.05 compared with saline-treated rats). The beneficial effects of U-63,557A and of SQ-29,548 were not accompanied by reduction in indices of myocardial oxygen demand (heart rate and arterial pressure). However, neutrophil accumulation in the infarcted myocardium was markedly decreased by U-63,557A and SQ-29,548 pretreatment. Myocardial myeloperoxidase activity, a specific marker of neutrophil infiltration, was also decreased (P less than 0.02) in U-63,557A- and SQ-29,548-treated animals (0.09 +/- 0.03 and 0.07 +/- 0.02 units/100 mg, respectively) compared with saline-treated infarcted rats (0.19 +/- 0.04 units/100 mg). In vitro incubation of U-63,557A and SQ-29,548 caused a significant and similar reduction in f-MLP-induced neutrophil chemotaxis, and U-63,557A increased prostacyclin formation in whole blood. These data suggest that reduction in the extent of myocardial injury by TXA2 synthetase or receptor inhibitors may, in part, relate to a decrease in neutrophil accumulation in the infarcted tissue. In spite of differences in mechanisms of action of U-63,557A and SQ-29,548, both agents exert a similar protective effect on the extent of myocardial injury following coronary ligation. Reduction in neutrophil accumulation in the infarcted zone, as well as in f-MLP-directed chemotaxis in vitro, suggests that TXA2 inhibition may modulate neutrophil migration.

Topics: Animals; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Chemotaxis, Leukocyte; Creatine Kinase; Epoprostenol; Fatty Acids, Unsaturated; Hydrazines; Male; Myocardial Infarction; Myocardium; Neutrophils; Peroxidase; Platelet Aggregation; Rats; Rats, Inbred Strains; Thromboxane A2; Thromboxane B2; Thromboxane-A Synthase

The complement cleavage product, C5a, causes a bronchoconstriction in the guinea pig as evidenced by a decrease in dynamic lung compliance and an increase in pulmonary resistance. Previous studies had demonstrated that the antihistamine pyrilamine and the cyclooxygenase inhibitor indomethacin inhibited the C5a-induced bronchoconstriction but the leukotriene (LT)D4 antagonist L-649,923 did not. As an extension of those studies, the purpose of the present study was to determine the contribution of specific cyclooxygenase products and/or LTB4 in mediating C5a-induced bronchoconstriction. To assess the role of the various potential mediators, plasma levels of thromboxane (TX)B2, prostaglandin (PG)D2 and PGF2 alpha were monitored. In addition, guinea pigs were treated either with the TX synthetase inhibitor U-63557A, treated with the TX receptor antagonist SQ 29,548 or made tachyphylactic to the bronchoconstrictor actions of LTB4. C5a challenge caused an increase in plasma concentrations of TXB2, which peaked before the maximum of the bronchoconstriction. However, no significant increase in plasma concentrations of PGD2 or PGF2 alpha was seen. Both U-63557A at 80 mg/kg and SQ 29,548 significantly inhibited the C5a-induced bronchoconstriction, whereas 10 mg/kg of U-63557A did not. The inability of 10 mg/kg of U-63557A to inhibit the response could be explained by both incomplete inhibition of TX synthesis as well as possibly by the increased plasma concentrations of the potent bronchoconstrictor PGD2, which occurred with C5a challenge in the presence of U-63557A. In animals tachyphylactic to LTB4, the maximum of the C5a-induced bronchoconstriction was no different from control.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Airway Resistance; Animals; Arachidonic Acid; Arachidonic Acids; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Bronchi; Complement C5; Complement C5a; Dinoprost; Fatty Acids, Unsaturated; Guinea Pigs; Hydrazines; Injections, Intravenous; Leukotriene B4; Lung; Prostaglandin D2; Prostaglandins D; Prostaglandins F; Thromboxane B2; Thromboxane-A Synthase

The present study examined the contribution of changes in the synthesis or degradation (or both) of renal eicosanoids to the alterations in renal hemodynamics observed in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Renal blood flow and glomerular filtration rate were markedly reduced in DOCA-salt hypertensive rats compared with values observed in control rats given water or saline to drink. The abnormalities in renal hemodynamics in the hypertensive rats were associated with an increase in the excretion of thromboxane B2, an increase in the release of thromboxane B2 from renal cortical tissue slices, and a diminished release of prostaglandin E2 (PGE2) from renal medullary tissue. Additionally, the urinary excretion of PGE2 and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and the release of 6-keto-PGF1 alpha from renal cortical and medullary tissue were elevated in rats with DOCA-salt hypertension. Since the excretion of PGE2 and 6-keto-PGF1 alpha and the release of 6-keto-PGF1 alpha by medullary tissue were also elevated in normotensive rats given 1% NaCl solution to drink, these latter changes probably were related to an elevation of sodium intake rather than to the development of hypertension. The functional significance of the alterations in the renal production of thromboxane in DOCA-salt hypertensive rats was evaluated by comparing the effects of a thromboxane synthesis inhibitor and a receptor antagonist on renal function in normotensive and DOCA-salt hypertensive rats. The administration of the thromboxane synthetase inhibitor furegrelate and the thromboxane receptor blocker SQ 29548 had no effect on renal hemodynamics in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzofurans; Body Water; Bridged Bicyclo Compounds, Heterocyclic; Desoxycorticosterone; Fatty Acids, Unsaturated; Hemodynamics; Hydrazines; Hypertension; Kidney; Male; Meclofenamic Acid; Prostaglandins; Rats; Rats, Inbred Strains; Renal Circulation; Sodium; Sodium Chloride; Thromboxanes