thromboxane-b2 and imidazole

The capacity of glial tumor cells to migrate and diffusely infiltrate normal brain compromises surgical eradication of the disease. Identification of genes associated with invasion may offer novel strategies for anti-invasive therapies. The gene for TXsyn, an enzyme of the arachidonic acid pathway, has been identified by differential mRNA display as being overexpressed in a glioma cell line selected for migration. In this study TXsyn mRNA expression was found in a large panel of glioma cell lines but not in a strain of human astrocytes. Immunohistochemistry demonstrated TXsyn in the parenchyma of glial tumors and in reactive astrocytes, whereas it could not be detected in quiescent astrocytes and oligodendroglia of normal brain. Glioma cell lines showed a wide range of thromboxane B2 formation, the relative expression of which correlated with migration rates of these cells. Migration was effectively blocked by specific inhibitors of TXsyn, such as furegrelate and dazmegrel. Other TXsyn inhibitors and cyclooxygenase inhibitors were less effective. Treatment with specific inhibitors also resulted in a decrease of intercellular adhesion in glioma cells. These data indicate that TXsyn plays a crucial role in the signal transduction of migration in glial tumors and may offer a novel strategy for anti-invasive therapies.

Topics: Arachidonic Acids; Aspirin; Astrocytes; Benzofurans; Brain Neoplasms; Cell Adhesion; Cell Movement; Enzyme Induction; Enzyme Inhibitors; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Glioma; GTP-Binding Proteins; Humans; Imidazoles; Indomethacin; Lysine; Models, Biological; Neoplasm Proteins; Neoplastic Stem Cells; Oligodendroglia; Pentanoic Acids; Phenotype; Pyridines; RNA, Messenger; RNA, Neoplasm; Signal Transduction; Thromboxane B2; Thromboxane-A Synthase; Tumor Cells, Cultured

Thromboxane, prostacyclin and their ratio could play an important role in the ischemic liver injury. To study this hypothesis, thromboxane and prostacyclin were measured by RIA after incubation of liver tissues removed during and after an ischemia of 90 min in male Wistar rats. The thromboxane to prostacyclin ratio increases during this period. In order to examine if this change could influence the survival rate of animals submitted to the same period of ischemia, drugs able to reduce the relative predominance of thromboxane were infused. The survival rate was not modified by administration of Iloprost or Daltroban, the antagonist of the thromboxane receptors. By contrast, imidazole, an inhibitor of thromboxane synthetase, significantly increased the survival rate. The same result was obtained with the administration of Daltroban plus Iloprost, suggesting that the reduction of thromboxane action associated with the increase of PGI2 level reduces the ischemic injury.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Epoprostenol; Iloprost; Imidazoles; Ischemia; Liver; Male; Phenylacetates; Rats; Rats, Inbred Strains; Sulfonamides; Thromboxane B2

This study tests whether activated complement leads to a selective entrapment of polymorphonuclear leukocytes (PMN's) in the lungs. Awake sheep were infused for 5 min with zymosan-activated plasma (ZAP, 2.5 mg/ml) at a rate of 5 ml/min into the superior vena cava (IV, n = 4) or intra-arterially into the aortic arch or femoral artery (IA, n = 8). At the end of IV infusion, leukocyte counts fell from 8,862 to 1,631/mm3 (P less than 0.01). PMN counts across the lungs decreased by 74%. There were increases in plasma thromboxane (Tx) B2 from 114 to 2,733 pg/ml (P less than 0.01), mean pulmonary arterial pressure from 12 to 42 mmHg (P less than 0.01), and physiological shunt from 13 to 25% (P less than 0.05). Within 1 h lymph TxB2 levels had risen from 301 to 4,916 pg/ml (P less than 0.01), lung lymph flow (QL) rose from 3.7 to 11.1 ml/30 min (P less than 0.05), lymph-to-plasma protein ratio (L/P) remained unchanged at 0.63, and lymph protein clearance increased from 2.3 to 7.5 ml/30 min (P less than 0.05). Leukosequestration, quantitated by capillary PMN counting and by assaying the granulocyte marker myeloperoxidase, occurred relative to sham animals (P less than 0.05) in the lung and spleen but not in other organs. Intra-arterial ZAP infusion led to changes that were similar in magnitude and timing to the IV group.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Blood Pressure; Complement Activation; Female; Imidazoles; Lung; Methacrylates; Neutrophils; Peroxidase; Sheep; Thromboxane B2; Zymosan

Previous studies have indicated that the regional distribution of the arachidonic acid metabolites around a focal ischemic lesion may be important in the pathogenesis of cerebral ischemia. To determine the functional significance of this regionalization, we examined the effect of imidazole (a thromboxane synthetase inhibitor) on the distribution of the vasoconstrictor thromboxane and the vasodilators prostacyclin and prostaglandin E2 (PGE2) and on the distribution of cerebral blood flow (CBF) around a focal ischemic lesion, middle cerebral artery (MCA) occlusion in the cat. The study was conducted in two phases. The first phase examined regional distribution of tissue arachidonic acid metabolites and the effect of imidazole treatment on that distribution. The second phase examined the effect of imidazole treatment on the distribution of blood flow about the focal ischemic lesion as well as on electrocortical function and edema production. MCA occlusion resulted in increased thromboxane, prostacyclin, and PGE2 levels in the ipsilateral hemisphere. These increases were greatest in the region of marginal ischemia and were present both 3 and 6 hours after occlusion. Imidazole pretreatment (50 mg/kg i.p.) significantly inhibited thromboxane production, but augmented production of prostacyclin and PGE2. In the blood flow studies, imidazole was without effect on regions of dense cerebral ischemia (CBF less than 20 ml/minute/100 g for more than 12 of 24 postocclusion hours). In regions of marginal ischemia (20 less than CBF less than 30 ml/minute/100 g for more than 12 of 24 postocclusion hours), imidazole pretreatment significantly increased blood flow in both gray and white matter compared with saline-treated controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Brain; Brain Edema; Cats; Cerebrovascular Circulation; Dinoprostone; Evoked Potentials, Somatosensory; Imidazoles; Ischemic Attack, Transient; Prostaglandins E; Thromboxane B2; Thromboxane-A Synthase

Although there are many data concerning the cytotoxic and immunosuppressive effects of antimetabolites such as azathioprine and 6-mercaptopurine, the mechanism of their antiinflammatory action has not been extensively investigated. In the present work, it is shown that azathioprine and 6-mercaptopurine (10-500 micrograms/ml) inhibit in a dose-dependent manner the production of PGE2, PGF2 alpha, 6-keto-PGF1 alpha and TXB2 by unseparated spleen cells as well as that of 6-keto-PGF1 alpha by adherent peritoneal macrophages. This inhibitory effect appears rapidly in vitro (within 15 min of incubation) and is observed in the presence of exogenous arachidonic acid (5 x 10(-6) M). The persistence of this effect in the presence of arachidonic acid, together with the fact that the production of four cyclooxygenase derivatives of acid arachidonic metabolism are inhibited, suggests that these drugs are acting at the cyclooxygenase level. The finding that cytotoxic and immunosuppressive agents, which act mainly by inhibiting RNA and DNA synthesis, can block prostaglandin production, may explain part of their antiinflammatory effects.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Azathioprine; Female; Imidazoles; In Vitro Techniques; Indomethacin; Male; Mercaptopurine; Mice; Mice, Inbred C57BL; Peritoneal Cavity; Prostaglandins; Radioimmunoassay; Spleen; Thromboxane B2

Recent studies with high frequency ventilation (HFV) have noted that HFV-induced increases in mean airway pressure leads to a marked cardiovascular depression, especially in cardiac output (CO). Aside from mechanical events a negative inotropic agent possibly prostaglandin in nature may also be involved. This study examined the possible involvement of thromboxane A2 (TXA2) in the HFV-induced cardiovascular deterioration. Chloralose-anesthetized mechanically-ventilated dogs were subjected to HFV 4, 10, and 20 mm Hg for 30 min. Some animals were also treated with imidazole (25 mg/Kg/hr) prior to HFV. Arterial levels of TXB2 (stable metabolite of TXA2) where monitored by radioimmunoassay. During HFV, tracheal pressure-related decreases in both CO and stroke volume (SV) were noted. Imidazole treatment significantly reduced the decrement in SV. Application of HFV resulted in variable changes in circulating TXB2 levels. Overall, application of HFV did not result in a significant change from baseline levels. Furthermore there was no correlation between changes in CO and SV with changes in arterial TXB2 concentration. These results do not support the hypothesis that hyperexpansion of the lungs during HFV causes the release of a cardiodepressant prostanoid.

Topics: Animals; Bicarbonates; Blood Pressure; Carbon Dioxide; Cardiac Output; Cardiovascular Physiological Phenomena; Cardiovascular System; Dogs; Female; Heart Rate; Hydrogen-Ion Concentration; Imidazoles; Male; Oxygen; Partial Pressure; Radioimmunoassay; Respiration; Thromboxane B2; Tidal Volume

The effect of OKY-046 (ONO, Japan), a selective TX inhibitor, was studied for its effect on uterine and platelet activity. On day 21 of pregnancy, rats were injected with either 0, 1, or 5 mg/kg OKY-046 via the tail vein. One hour following injections, in vitro activity of uteri and platelets was assessed. A decrease (P less than .01) in uterine TXB2 production (measured by RIA) occurred with increasing OKY-046 dose (104 +/- 31 vs 44 +/- 6 vs 24 +/- 2 ng TXB2/g tissue/45 min). OKY-046 treatment had no effect on other prostanoids. Contractile activity was not affected by OKY-046. The amount of TXB2 produced in platelets from OKY-046 (5 mg/Kg) treated rats was 45.5% less than that from controls (P less than .001). Likewise, arachidonate-induced aggregation of platelets from OKY-046 treated rats was 46.1% less (P less than .05) than that of controls. In summary, in vivo administration of OKY-046 selectively reduced uterine TXB2 without altering other prostanoids, or affecting uterine contractions. In contrast, both platelet TXB2 production and platelet function (aggregation) was decreased.

Topics: 6-Ketoprostaglandin F1 alpha; Acrylates; Animals; Blood Platelets; Dinoprost; Dinoprostone; Female; Imidazoles; Methacrylates; Pregnancy; Pregnancy, Animal; Prostaglandins; Prostaglandins E; Prostaglandins F; Rats; Rats, Inbred Strains; Thromboxane B2; Thromboxanes; Uterus

Twenty-four hours of complete unilateral ureteral obstruction (UUO) produces intense renal vasconstriction in the rat even after release of obstruction. In the ex vivo perfused hydronephrotic rabbit kidney, bradykinin stimulates increased production of the vasoconstrictor autocoid thromboxane. In the present study, we measured basal and bradykinin-stimulated thromboxane and prostaglandin E2 production by UUO and contralateral rat kidneys perfused ex vivo. Furthermore, we evaluated thromboxane synthetase inhibition by imidazole and by two of its substituted derivatives, UK 37248 and UK 38485, in vitro. We compared these in vitro findings with in vivo measurements of renal hemodynamics and excretory function before and after the intrarenal artery administration of thromboxane synthetase inhibitors. Both basal and bradykinin-stimulated thromboxane and prostaglandin E2 production were significantly increased in hydronephrotic kidneys. Imidazole and its substituted congeners were effective inhibitors of bradykinin-stimulated thromboxane B2 production in vitro. However, the substituted imidazoles were more potent, more efficacious, and more selective for thromboxane synthetase inhibition than the parent compound. In vivo, administration of imidazole into the renal artery of the UUO kidney improved function slightly, whereas administration of UK 37248 or UK 38485 doubled renal blood flow and excretory function but did not restore them to normal. We conclude that the hydronephrotic rat kidney produces increased amounts of the vasoconstrictor eicosanoid thromboxane and that thromboxane is an important mediator of vasoconstriction in this model of disease.

Topics: Animals; Dinoprostone; Dose-Response Relationship, Drug; Hydronephrosis; Imidazoles; Methacrylates; Prostaglandins E; Rats; Rats, Inbred Strains; Thromboxane B2; Thromboxane-A Synthase; Ureteral Obstruction

Acute renal failure (ARF) was induced in 35 week-old conscious female Wistar rats, by intramuscular (IM) injection of glycerol. Intraperitoneal (IP) injection of imidazole, an inhibitor of thromboxane (TXA2) synthesis, partially protected the animals against ARF. This protection was accompanied by a significant decrease in renal TXB2 (the stable chemical metabolite of TXA2) and a significant increase in renal 6-keto-PGF1 alpha (the stable chemical metabolite of PGI2) synthesis. Intraperitoneal injection of captopril (SQ 14225) an angiotensin-converting-enzyme inhibitor, did not protect the animals against ARF. This lack of protection was accompanied by a significant increase in renal TXB2 and a significant decrease in renal 6-keto-PGF1 alpha synthesis. The results suggest that: (a) the renin-angiotensin (R-A) system does not play a role, or has only a secondary one in the development of ARF; (b) thromboxane A2 (the most potent vasoconstrictor and platelet aggregator agent known) is the preponderant agent responsible for the development of this pathological syndrome.

Topics: 6-Ketoprostaglandin F1 alpha; Acute Kidney Injury; Angiotensin II; Animals; Captopril; Dinoprostone; Female; Glycerol; Imidazoles; Prostaglandins; Prostaglandins E; Rats; Thromboxane A2; Thromboxane B2; Thromboxanes

Lewis lung primary carcinomas have been extracted for eicosanoids, and the findings examined in relation to lung metastases. The order of the 5 compounds measured was PGE2 greater than PGE1 greater than PGF2 alpha greater than 6-keto-PGF1 alpha greater than TXB2. On the basis of the observation that the balance of PGI2 and TXA2 is altered in metastasis (Honn et al., 1983), the effects of Nafazatrom, a PGI2 enhancing agent, and imidazole, a thromboxane synthetase inhibitor, were tested. The experimental approach taken was to study spontaneous lung metastases after removal of the primary tumour at 13 days after tumour cell inoculation. Both Nafazatrom and imidazole decreased the lung weight when given during the period either before or after the excision of the primary tumour. There was a general trend toward an increase in the number of small lung nodules (greater than 2 mm) and a decrease in large lung nodules (greater than 2 mm) as a result of the chemotherapy. Mean survival time of the mice was significantly different among the five groups, with the mice surviving the longest in the group treated with Nafazatrom after the excision of the primary tumour.

Topics: Animals; Body Weight; Carcinoma; Imidazoles; Lung; Lung Neoplasms; Mice; Neoplasm Metastasis; Organ Size; Prostaglandins; Prostaglandins E; Prostaglandins F; Pyrazoles; Pyrazolones; Thromboxane B2

We demonstrated that potassium depletion significantly increased gentamicin nephrotoxicity in Sprague-Dawley rats (100 mg X kg-1 X day-1). To determine whether this enhanced toxicity was mediated by renin secretion, we evaluated the effect of a converting enzyme inhibitor in this model. When we administered the combination of captopril (100 mg X kg-1 X day-1) and gentamicin in potassium-depleted rats, we observed a surprising and significant adverse effect of this combination on the clearances of inulin (CIn) and PAH (CPAH) and renal blood flow (RBF). Pretreatment with indomethacin significantly improved CIn and CPAH, and potassium repletion abolished this effect entirely. In potassium-depleted animals that received both gentamicin and captopril, the intra-arterial administration of imidazole, a thromboxane synthetase inhibitor, significantly reduced urinary TXB2 excretion and significantly improved RBF and CIn in vivo. In the same group of animals, administration of the kallikrein antagonist aprotinin also significantly increased both RBF and CIn. To measure total renal thromboxane B2 production (TXB2), we perfused kidneys ex vivo with cell-free perfusate. Three groups of animals were studied: potassium-repleted control animals, potassium-depleted control animals, and potassium-depleted animals treated with gentamicin alone, captopril alone, or the combination of gentamicin and captopril. We measured TXB2 in renal venous effluent by radioimmunoassay. Ex vivo perfused kidneys from potassium-depleted control animals produced significantly more TXB2 than potassium-repleted controls. Kidneys from potassium-depleted animals that received both gentamicin and captopril produced significantly greater amounts of TXB2 than did kidneys from potassium-depleted animals treated with captopril alone, gentamicin alone, or control potassium-depleted kidneys. The administration of imidazole ex vivo at a rate equivalent to in vivo administration (10 microM/min) reduced TXB2 production by potassium-depleted kidneys that received the combination of gentamicin and captopril to that of potassium-repleted control kidneys. These results suggest that the deleterious effect of captopril in potassium-depleted rats that received gentamicin is due at least in part to kinin-stimulated renal TXB2 production.

Topics: Aminoglycosides; Angiotensin-Converting Enzyme Inhibitors; Animals; Aprotinin; Captopril; Gentamicins; Imidazoles; Indomethacin; Inulin; Kidney; Kidney Function Tests; Male; p-Aminohippuric Acid; Potassium Deficiency; Radioimmunoassay; Rats; Rats, Inbred Strains; Renal Circulation; Renin; Thromboxane B2

Previous studies have suggested an important role of thromboxane (Tx) in the pathogenesis of endotoxin shock in the rat. The present study evaluated the role of thromboxane in an LD70 primate model of endotoxin shock by administering 6 mg/kg of endotoxin to three groups of animals that were pretreated with either saline (5 ml), OKY 1581 (2 mg/kg, 10 min prior), or imidazole (25 mg/kg/hr starting 30 min prior), groups I, II, and III, respectively. There were significant differences between the groups with respect to changes in MAP, PAP, and CO. OKY 1581 effectively blocked endotoxin-induced increase in plasma Tx. However, as a result of shunting of the endoperoxides into the prostacyclin pathway, there was a greater increase in plasma 6-keto PGF1 alpha, the stable hydrolysis product of prostacyclin. Imidazole augmented the formation of both prostacyclin and Tx. Despite the differences in plasma prostanoids, there was no difference between the groups with respect to changes in platelet or WBC counts, nor in survival: I (4/10); II (4/10); III (2/6).. (i) endotoxin-induced neutropenia and decrease in the platelet count are not Tx mediated; (ii) Tx is not solely responsible for the decrease in CO during endotoxin shock; (iii) it is possible to prevent endotoxin-induced increase in the PAP by either blocking Tx formation or by increasing endogenous PGI2 production; and (iv) Tx may not be a major contributing factor in the mortality of endotoxin shock in baboons.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Hemodynamics; Imidazoles; Leukocyte Count; Male; Methacrylates; Papio; Random Allocation; Shock, Septic; Thromboxane B2; Thromboxane-A Synthase; Thromboxanes; Time Factors

The excretion rates of renal thromboxane B2 (TXB2) and 6-ketoPGF1 alpha, the stable chemical metabolites of thromboxane A2 (TXA2) and prostaglandin I2 (PGI2) respectively, PGE2 and sodium were determined in normal and saline-loaded rats treated with the thromboxane synthetase inhibitor imidazole. In normal rats the administration of imidazole in doses which did not affect renal 6-keto-PGF1 alpha and PGE2 excretion but selectively inhibited renal TXB2 excretion, significantly increased the sodium excretion rate. Volume expansion with saline increased renal PGE2 and 6-ketoPGF1 alpha excretion but did not alter renal TXB2 excretion. The increase in renal prostaglandin excretion was accompanied by an increased sodium excretion rate. The administration of imidazole to saline-loaded animals also decreased renal TXB2 excretion but did not alter the increased excretion of renal PGE2 and 6-ketoPGF1 alpha. This reduction in renal thromboxane biosynthesis by imidazole further increased the sodium excretion rate. We suggest that TXA2 is a potent antinatriuretic factor as well as the most potent vasoconstrictor agent known.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Dinoprostone; Epoprostenol; Imidazoles; Kidney; Male; Prostaglandins E; Rats; Rats, Inbred Strains; Sodium; Sodium Chloride; Thromboxane A2; Thromboxane B2; Thromboxanes

We determined the effects of extracorporeal perfusion with a constant flow (75 ml . min-1 . kg-1) of autologous blood on hemodynamics and fluid balance in sheep lungs isolated in situ. After 5 min, perfusate leukocyte and platelet counts fell by two-thirds. Pulmonary arterial pressure (Ppa) increased to a maximum of 32.0 +/- 3.4 Torr at 30 min and thereafter fell. Lung lymph flow (QL), measured from the superior thoracic duct, and perfusate thromboxane B2 (TXB2) concentrations followed similar time courses but lagged behind Ppa, reaching maxima of 4.1 +/- 1.2 ml/h and 2.22 +/- 0.02 ng/ml at 60 min. Lung weight gain, measured as the opposite of the weight change of the extracorporeal reservoir, and perfusate 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) concentration increased rapidly during the first 60 min and then more gradually. After 210 min, weight gain was 224 +/- 40 g and 6-keto-PGF1 alpha concentration, 4.99 +/- 0.01 ng/ml. The ratio of lymph to plasma oncotic pressure (pi L/pi P) at 30 min was 0.61 +/- 0.06 and did not change significantly. Imidazole (5 mM) reduced the changes in TXB2, Ppa, QL, and weight and platelet count but did not alter 6-keto-PGF1 alpha, pi L/pi P, or leukocyte count. Indomethacin (0.056 mM) reduced TXB2, 6-keto-PGF1 alpha, and the early increases in weight, Ppa, and QL but did not alter the time courses of leukocyte or platelet counts. Late in perfusion, however, Ppa and QL were greater than in either untreated or imidazole-treated lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Epoprostenol; Hypertension, Pulmonary; Imidazoles; Indomethacin; Lung; Lymph; Organ Size; Perfusion; Pulmonary Circulation; Sheep; Thromboxane B2; Time Factors; Water-Electrolyte Balance

The effect of the thromboxane (TX) synthase inhibitors dazoxiben and imidazole on platelet activation by endogenous and exogenous arachidonic acid (AA) was tested with human washed platelets. Dazoxiben (1-20 microM) inhibited the formation of TXB2 and markedly enhanced the shape change, aggregation, and (3H)serotonin release induced by added AA or when prostaglandin synthesis from endogenous AA was triggered by collagen, hydrogen peroxide or methyl mercury chloride (methyl-Hg). Platelet activation by hydrogen peroxide (20-1200 microM) or methyl-Hg (1-5 microM) was entirely dependent on endogenous prostaglandin (PG) synthesis since acetylsalicylic acid (ASA), indomethacin or the cyclic endoperoxide/TXA2-antagonist BM 13.177 counteracted these stimulants with and without dazoxiben. Apparently, the potentiation is due to accumulating cyclic endoperoxides which during TX synthase inhibition reach greater platelet-activating potency than TXA2. Albumin or human platelet-poor plasma inhibited the platelet activation by hydrogen peroxide and methyl-Hg and suppressed the potentiation by dazoxiben. The latter effect of albumin may result from its PGD isomerase activity which redirects the cyclic endoperoxide metabolism to the platelet-inhibitory PGD2. The results show that non-platelet factors such as albumin are necessary to prevent a potentiating effect of TX synthase inhibitors on platelet activation.

Topics: Arachidonic Acid; Arachidonic Acids; Blood Platelets; Collagen; Drug Interactions; Humans; Hydrogen Peroxide; Imidazoles; In Vitro Techniques; Indomethacin; Methylmercury Compounds; Oxidoreductases; Platelet Aggregation; Serotonin; Serum Albumin; Sulfonamides; Thromboxane B2; Thromboxane-A Synthase

Whereas numerous studies have investigated the role of prostacyclin and thromboxane A2 in the maintenance of coronary blood flow, most of these have focused on normal vessels. In the present investigation, we examined the prostaglandin- and thromboxane-synthesizing capacity of isolated coronary artery segments obtained from the site of a critical coronary artery stenosis. Cyclic flow variations were produced by placing a hard cylindrical constrictor on the proximal left anterior descending coronary artery in open-chest, anesthetized dogs. Cyclic flow variations are characterized by progressive declines in coronary blood flow, interrupted by sudden spontaneous restorations of flow. After cyclic flow variations had been induced, the hearts were removed, and the left anterior descending and circumflex coronary arteries were dissected. The vessels were cut into segments and incubated in the presence of increasing concentrations of arachidonic acid (10(-4)-10(-6) M). The synthesis of prostaglandin E2, thromboxane B2, and 6-keto prostaglandin F1 alpha by the coronary segments was measured by radioimmunoassay. When incubated in the presence of 10(-5) M arachidonic acid, coronary artery segments obtained from the left anterior descending coronary artery undergoing cyclic flow variations produced substantially more thromboxane B2 (142 +/- 27 vs. 29 +/- 3 pg/mg P less than 0.01) and less 6-keto prostaglandin F1alpha (125 +/- 12 vs. 350 +/- 30 pg/mg, P less than 0.01) than control circumflex coronary artery segments. Circumflex coronary vessels in which the endothelium was removed ex vivo produced 6-keto prostaglandin F1alpha levels comparable to those found in the left anterior descending coronary artery (147 +/- 17 pg/mg), but did not synthesize thromboxane B2 (23 +/- 2.6 pg/mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Aortic Valve Stenosis; Arachidonic Acid; Arachidonic Acids; Chromatography, High Pressure Liquid; Coronary Circulation; Coronary Vessels; Dinoprost; Dinoprostone; Dogs; Epoprostenol; Imidazoles; Male; Platelet Aggregation; Prostaglandins E; Prostaglandins F; Regional Blood Flow; Thromboxane A2; Thromboxane B2; Thromboxanes

A reproducible electrical injury to the hind limb was produced in rats, an injury characterized by progressive tissue necrosis. Serial histochemical examinations of cross sections with a peroxidase-antiperoxidase method revealed increased production of arachidonic acid metabolites, especially thromboxane, at distal sites near the entrance wound and in periosseous tissues more proximally. Levels of these vasoactive substances remained elevated during the time of progressive necrosis and demarcation of seemingly normal, uninjured tissue. Treatment with agents capable of blocking thromboxane production allowed tissue salvage, as evidenced by a decreased autoamputation rate and an increased total surviving length. From this study it appears that an electrical injury is thermal trauma, producing elevated levels of arachidonic acid metabolites in areas of greatest heat production. Prolonged thromboxane excess, with resultant vasoconstriction and thrombosis in the microcirculation, is seen to play a key role in the progressive tissue loss characteristic of the injury. The use of antithromboxane agents may be of benefit in halting this progression and salvaging tissue in these devastating injuries.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Burns, Electric; Dinoprost; Dinoprostone; Imidazoles; Male; Prostaglandins E; Prostaglandins F; Rats; Rats, Inbred Strains; Thromboxane B2

Platelet aggregation is known to be increased in diabetes mellitus, and the enhanced thromboxane production has been shown to be one of the causes of such abnormal platelet function. To investigate which step is activated in diabetic prostaglandin metabolism, three specific inhibitors of prostaglandin synthetases were used in this study, which were mepacrine, indomethacin and imidazole. Platelet aggregation induced by collagen was significantly increased accompanying enhanced thromboxane production in diabetics with proliferative retinopathy compared with age matched controls. Platelet aggregation in diabetics with proliferative retinopathy was less inhibited by the addition of each inhibitor compared with controls. However, there was no difference in inhibitory pattern of platelet aggregation among the three inhibitors. In addition, thromboxane production during aggregation in diabetics with proliferative retinopathy was significantly greater than that in controls by the addition of each inhibitor. Inhibitory patterns of thromboxane production did not differ among the addition of three inhibitors. It is concluded that enhanced thromboxane production resulting in enhanced platelet aggregation would be related to diabetic vascular complications. This abnormal prostaglandin production can be due to the activation of general steps in prostaglandin metabolism in diabetic platelets, not of a specific enzyme.

Topics: Adult; Diabetes Mellitus; Diabetic Retinopathy; Female; Humans; Imidazoles; Indomethacin; Male; Middle Aged; Platelet Aggregation; Quinacrine; Thromboxane B2; Thromboxanes

Differences in the vascular response to burn and freeze injuries were investigated as a model for defining the mechanism and cause of vascular occlusion in rats after dermal burns. Concentrations of thromboxane and prostacyclin in wound fluid were elevated in both types of trauma. However, inhibition of prostaglandin synthesis by indomethacin failed to promote vascular patency in burn-injured animals. However, the systemic administration of ibuprofen and imidazole led to increased vascular patency. Ibuprofen promoted vascular patency even when given six hours after burn trauma. These studies indicate that ibuprofen and imidazole promote vascular patency by fostering fibrinolysis rather than by inhibiting prostaglandin synthesis and release.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Blood Vessels; Body Fluids; Burns; Fibrinolysis; Freezing; Ibuprofen; Imidazoles; Indomethacin; Prostaglandin Antagonists; Rats; Rats, Inbred Strains; Skin; Thromboxane B2; Time Factors; Wound Healing

Thromboxane B2 (TXB2), along with other primary prostaglandins, was synthesized when rat liver microsomes were incubated with radioactive arachidonic acid. TXB2 was identified directly by chemical ionization mass spectrometry and indirectly by using specific inhibitors of TX synthetase, viz., imidazole and OKY-1555 ((E)-3(4-(3-pyridyl-methyl) phenyl)-2 methyl acrylic acid HCl). The supernatant fraction obtained after centrifugation at 105,000 X g for 60 min contained a possible regulatory component that suppressed thromboxane synthesis. The regulatory influence is lost after partial hepatectomy.

Topics: Animals; Chromatography, Thin Layer; Cytosol; Female; Imidazoles; Liver; Mass Spectrometry; Methacrylates; Microsomes, Liver; Rats; Thromboxane B2; Thromboxanes

Topics: Animals; Escherichia coli Infections; Imidazoles; Kinetics; Male; Radioimmunoassay; Rats; Rats, Inbred Strains; Sepsis; Thromboxane B2; Thromboxanes

The larval stage of the tapeworm, Taenia taeniaeformis, was incubated in different concentrations of arachidonic acid. At various times after incubation, aliquots were removed for bioassay on either 38 microM aspirin or non-aspirin-treated equine platelets and by radioimmunoassay for the thromboxane A2 breakdown product, thromboxane B2 (TXB2). Platelet agonist activity was detected as early as 30 sec after addition of the arachidonic acid. In aspirin-treated platelets, this agonist activity peaked at 1 to 4 min and thereafter decayed rapidly with a time course that was both worm and arachidonic acid dependent. When assayed on non-aspirin-treated platelets the agonist activity was again detectable as early as 30 sec after addition of arachidonic acid, peaked at 1 to 3 min and then decayed very slowly over a 30-min period of incubation. It was found that levels of TXB2 were detected which increased over time concomitant with the decay of the platelet agonist activity. The most consistent detection of TXB2 generation was at 30 min with a mean of 49.6 pg and a range of 22.1 to 84.8 pg for four experiments. This report presents the first evidence for arachidonic acid utilization by a cestode or trematode and could in part provide an explanation for the marked cellular inflammation noted around dead or dying parasites.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Aspirin; Horses; Imidazoles; Indomethacin; Kinetics; Larva; Platelet Aggregation; Rats; Taeniasis; Thromboxane A2; Thromboxane B2; Thromboxanes

Levels of prostaglandin (PG) E2 and thromboxane (TX) B2, the stable metabolite of TXA2, were measured by radioimmunoassay in cerebrospinal fluid (CSF) collected from the third ventricle and the cisterna magna of conscious cats. In the absence of fever, PGE2 was usually below the threshold of the assay (0.05-0.37 ng/ml), while TXB2 was measurable in the majority of cases and its concentration was greater in the third ventricle (about 0.7 ng/ml) than in the cisterna magna (about 0.2 ng/ml). At either site, TXB2 content rose if any manipulation was required for the collection of samples. PGE2 levels increased to measurable values (max 1.1-1.4 ng/ml) during fever produced by intrathecal or intravenous administration of leucocytic pyrogen. In contrast, TXB2 concentration rose to an average of 2.2-4 ng/ml only when pyrogen (bacterial or leukocytic) was given intrathecally. Moreover, TXB2 elevation, unlike PGE2 elevation, was limited to the uprise phase of the fever. Imidazole, given either intraperitoneally (50 mg/kg) or intrathecally (3 mg), attenuated the pyrogen fever and suppressed any rise in TXB2 levels. At the same time, the drug tended to increase the PGE2 content of the CSF. Evidence was also obtained suggesting that a fraction of PGE2 is bound to CSF protein, and this event may be important to the inactivation of the compound. These findings are consistent with the concept that PGE2 is involved in the sequence of events underlying pyrogen fever. A role for thromboxane A2 in this process remains to be established.

Topics: Animals; Body Temperature; Cats; Dinoprostone; Female; Fever; Imidazoles; Interleukin-1; Male; Prostaglandins E; Proteins; Pyrogens; Radioimmunoassay; Reference Values; Thromboxane B2; Thromboxanes

Thromboxane (TX) has been reported to cause mortality in endotoxin or septic shock. Cyclooxygenase inhibition improves survival in gram-negative or gram-positive shock. The exact level in the prostaglandin system of which the protection occurs is unknown. This study was designed to compare the effects of a cyclooxygenase inhibitor (indomethacin, IND) to a thromboxane synthetase inhibitor (IMI) on survival and on the production of Tx and prostacyclin (PGI2) in a clinically relevant rat gram-negative sepsis model. Three groups were studied: 1) control (N = 35) animals received E coli only; 2) IND (N = 35) treated animals received 3 mg/kg IP; 3) IMI (N = 35) treated animals received 30 mg/kg IP. All drugs were given 1 h after an IP injection of E coli (LD70) organisms. In this model only IND significantly improved survival. IND and IMI significantly blocked the production of Tx seen in septic shock. IND blocked PGI2 production whereas IMI increased the production. These results show that Tx may not be important in the irreversible stages of shock. Shunting prostaglandin production to PGI2 with thromboxane synthetase inhibitors needs to be considered when using this group of compounds. The mechanism of protection by IND remains unknown.

Topics: Animals; Depression, Chemical; Imidazoles; Indomethacin; Male; Oxidoreductases; Prostaglandins F; Rats; Rats, Inbred Strains; Shock, Septic; Thromboxane B2; Thromboxane-A Synthase

The production of prostaglandin E2- (PGE2) like and thromboxane A2-(TXA2) like substances is increased after release of unilateral ureteral obstruction (UUO) for 3 days in the isolated perfused rabbit kidney. It has been postulated that this increase in TXA2 biosynthesis might contribute to the development of vasoconstriction in the obstructed kidney. In the present studies, the production of TXA2 and PGE2 in the kidney was further investigated in rats after UUO for 2-18 h. Radioimmunoassay was used to determine thromboxane B2 (TXB2), a chemically stable metabolite of TXA2, and PGE2 production during the incubation of renal slices in vitro. Unlike previous studies, an increase in TXB2 and PGE2 production was demonstrable in the obstructed kidney even in the absence of pharmacological stimulation by bradykinin or angiotensin II. The effect of UUO on prostaglandin production differed in the different anatomical parts of the kidney. In the papilla, production of both TXB2 and PGE2 was increased in the obstructed kidney. In the cortex, however, UUO had a stimulatory effect only on TXB2 production but not on PGE2 production. The increase in TXB2 and PGE2 production was demonstrable as early a 2 h (tested) after ureteral obstruction. Prolongation of ureteral obstruction for 18 h diminished the stimulatory effect of UUO on PGE2 production but not on TXB2 production.

Topics: Animals; Dinoprostone; Imidazoles; Indomethacin; Kidney; Male; Prostaglandins E; Radioimmunoassay; Rats; Thromboxane B2; Thromboxanes; Time Factors; Ureteral Obstruction

Imidazole has been proposed to reverse renal vasoconstriction following unilateral obstruction, presumably through blockade of thromboxane A2 (TXA2) synthesis. We examined this hypothesis in rats subjected to unilateral ureteral obstruction for 24 h by 1) performing renal function studies before and during imidazole infusion, and 2) measuring TXB2 and prostaglandin E2 (PGE2) in urine collected before and during imidazole infusion and the profile of products generated by metabolism of arachidonic acid with renal microsomes in vitro. Imidazole infusion was associated with only a bicarbonaturia in the postobstructed kidney; in contrast, clearance of PAH and inulin, fractional sodium excretion, and bicarbonate excretion were all increased in the contralateral kidney. In the postobstructed and contralateral kidneys, TXB2 excretion was diminished and PGE2 excretion was variable not only following imidazole infusion but after saline infusion as well. The profile of products generated by renal microsomal metabolism of arachidonic acid was similar among obstructed, contralateral, and normal kidneys. These results do not support the proposal that TXA2 is the mediator of renal vasoconstriction following unilateral ureteral obstruction.

Topics: Animals; Functional Laterality; Imidazoles; Kidney; Kinetics; Male; p-Aminohippuric Acid; Prostaglandin-Endoperoxide Synthases; Prostaglandins E; Rats; Thromboxane B2; Ureter

Cyclooxygenase inhibitors prevent the pulmonary vasomotor changes in response to low-dose endotoxin. We, therefore, explored the role of two highly vasoactive prostanoids, thromboxane A(2), a vasoconstrictor, and prostacyclin, a vasodilator, in the transient pulmonary vasoconstriction and subsequent loss of alveolar hypoxis vasoconstriction (AHPV) that follows endotoxin. AHPV was tested in the dog with a double-lumened endotracheal tube allowing ventilation of one lung with nitrogen as a hypoxic challenge while the other lung was ventilated with oxygen to maintain systemic oxygenation. Relative distribution of perfusion to the two lungs was assessed with intravenous (133)Xe and external scintillation detectors. The stable metabolites of thromboxane and prostacyclin, i.e., thromboxane B(2) and 6-keto-prostaglandin F(1alpha) were measured in plasma with radioimmunoassay. 15 mug/kg i.v. of endotoxin induced no rise in pulmonary vascular resistance (PVR), but prevented AHPV so that the initial 33% (+/-2 SEM) decrease in perfusion to the hypoxic lung became only a 2% (+/-1) decrease. Circulating levels of thromboxane and prostacyclin concurrently rose (P < 0.01) from nondetectable levels to 380 pg/ml (+/-40) and 360 pg/ml (+/-130). 150 mug/kg of endotoxin induced a transient rise in PVR from 4.09 to 9.00 mm Hg/liter per min in association (r = 0.89, P < 0.01) with a sharp rise in thromboxane levels to 4,460 pg/ml (+/-1,350) whereas prostacyclin levels were elevated less markedly to 550 pg/ml (+/-400). Prostaglandin F(2alpha), another vasoconstrictor, was not elevated. 30 min after endotoxin when PVR was again base line and AHPV lost, thromboxane fell significantly (P < 0.01) to 2,200 pg/ml (+/-1,100) whereas prostacyclin remained elevated at 360 pg/ml (+/-135), a level similar to that seen when 15 mug/kg of endotoxin induced loss of AHPV. Indomethacin prevented the rise in thromboxane and prostacyclin after endotoxin as well as the changes in pulmonary vasomotor tone. Thus, a complex interaction between thromboxane and prostacyclin is involved in the pulmonary vasomotor response to low-dose endotoxin.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Dogs; Endotoxins; Epoprostenol; Escherichia coli; Hemodynamics; Imidazoles; Prostaglandins; Prostaglandins F; Pulmonary Circulation; Thromboxane A2; Thromboxane B2; Thromboxanes

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Aspirin; Dogs; Female; Hemodynamics; Imidazoles; Indomethacin; Male; Myocardial Contraction; Positive-Pressure Respiration; Prostaglandins; Thromboxane B2