Effects of misoprostol on human circulation

Prostaglandins (PGs) of the E-type are potent vasodilators in most species and in most vascular beds. However, vasoconstrictor effects of PGEs have also been noted at selected sites. This study examined the effects of misoprostol, a PGE₁ analog with antiulcer activity, on the human cardiovascular system. Twenty healthy subjetcs participated in this double-blind, placebo-controlled, parallel group study. Following a 12 hour fast, heart rate, arterial blood pressure, light reflex plethysmography of the finger, resting blood flow volume in the lower arm and leg and peripheral vascular resistance were measured at 10 min. intervals for 1 hour prior to drug administration, to permit calculating baseline values. Misoprostol (400 mcg) or its matching placebo were administered orally, and the measurements were repeated at 10 min. intervals over the next 2 hours. A decrease in leg blood flow volume and a corresponding increase in leg peripheral vascular resistance were noted in the misoprostol group. A statistically significant decrease in heart rate between the two treatment groups was also noted. These small changes were not considered to be of clinical importance. No adverse experiences were reported. In conclusion, a single dose of misoprostol (400 mcg) has no clinically significant vasoconstrictive or vasodilative properties in man.     

Leukotriene C4 action and metabolism in the isolated perfused bullfrog heart

The effects of leukotrienes (LTs) have been widely studied in the isolated perfused mammalian heart; however, little is known about the effect or metabolism of LTs in the isolated bullfrog heart. Isolated perfused bullfrog hearts were administered randomized doses of LTC4, LTD4, or LTE4. The cardiac parameters of heart rate, developed tension, and its first derivative (dT/dt) were recorded. LTC4 was the most potent of the leukotrienes tested in eliciting positive inotropic effects. LTD4 and LTE4 were equally effective but about one order of magnitude less potent than LTC4. None of the LTs showed any chronotropic effects in this preparation. A series of [3H]LTC4 metabolism experiments were carried out using whole perfused hearts and minced bullfrog heart tissue. Isolated perfused bullfrog hearts administered [3H]LTC4 converted significant amounts to [3H]LTD4, and to a lesser degree, [3H]LTE4, during the 6-min course of collection. Both minced atrial and ventricular tissue converted [3H]LTC4 to radioactive metabolites that co-migrated with authentic LTD4 and LTE4 standards. In both tissues, the major product was [3H]LTD4, with smaller amounts of [3H]LTE4 produced. The atrium converted significantly more [3H]LTC4 to its metabolites than did the ventricle. The metabolism of [3H]LTC4 to [3H]LTD4 by both tissues was virtually abolished in the presence of serine borate. Cysteine had no effect on [3H]LTE4 production. The data in this study demonstrate that leukotrienes have the opposite inotropic effect on the heart when compared with mammals. Also in contrast to mammals, frogs metabolize LTC4 to a less potent compound and may use the LTC4 to LTD4 conversion as a mechanism of LTC4 inactivation.     

Urinary leukotriene E4 excretion is increased in type 1 diabetic patients: a quantification by liquid chromatography-tandem mass spectrometry

OBJECTIVE: Diabetes mellitus is associated with inflammatory state and increased cardiovascular mortality. Leukotrienes are arachidonic acid metabolites derived from the 5-lipoxygenase pathway that possess vasoactive, chemotactic and proinflammatory properties. The aim of this study was to evaluate (1) the urinary excretion of leukotriene E4 (LTE4) in type 1 diabetic subjects and healthy volunteers and (2) the influence of glycemic control attested by HbA(1C) on LTE4 excretion. METHODS AND RESULTS: Urinary excretion of LTE(4), measured by liquid chromatography-tandem mass spectrometry, was significantly (P=0.033) increased in diabetic patients (median [10th-90th percentiles]: 42.1 pg/mg creatinine [16.7-71.4], n=34), compared to healthy subjects (25.5 pg/mg creatinine [13.9-54.1], n=28). Subgroup analysis indicated a trend towards increased LTE4 excretion in patients with poor glycemic control [(HbA(1C)> or =9% or plasma glucose >18 mmol/L): 43.3 pg/mg creatinine [21.6-70.5], n=14], whereas no difference was observed between patients with good metabolic control [(HbA(1C)< or =7.5%): 36.4 pg/mg creatinine [15.8-83.4], n=20] and healthy subjects. CONCLUSIONS: This study suggested that increased LTE4 excretion in type 1 diabetic state might reflect systemic activation of the 5-lipoxygenase pathway. It could be a determinant of underlying inflammatory state and vascular disease.     

2-nor-leukotriene analogs: antagonists of the airway and vascular smooth muscle effects of leukotriene C4, D4 and E4

A structural analog of LTD4, 4R-hydroxy-5S-cysteinylglycyl-6Z-nonadecenoic acid (4R, 5S, 6Z-2-nor-LTD1) has been synthesized and pharmacologically characterized. It significantly antagonized the contractile action of LTD4, LTC4 and LTE4 in guinea pig airways. In addition, this compound antagonized the in vitro vasoconstrictive effects of LTD4 in the guinea pig pulmonary artery. The study of a series of structural analogs of 4R, 5S, 6Z-2-nor-LTD1 suggests that the spatial separation of the C-1 (eicosanoid) carboxyl relative to the hydroxyl is a critical determinant in LTD4 agonist/antagonist activity.     

Leukotriene E4 elimination and metabolism in normal human subjects

Radiolabeled leukotriene (LT) E4 was infused into three healthy subjects in order to assess the production and elimination of sulfidopeptide leukotriene metabolites in urine. Three different radiolabeled tracers were employed, [14,15-3H]LTE4, [35S]LTE4, and [14C] LTE4 in five separate infusion studies. There was a rapid disappearance of radioactivity from the vascular compartment in an apparent two-phase process. The first elimination phase had an apparent half-life of approximately 7 min. Radioactivity quickly appeared in the urine with 10-16% eliminated during the first 2 h following intravenous infusion; 7%, 2-5 h; 4%, 5-8 h; 4%, 8-15 h; and 1.5%, 15-24 h from the [14C] LTE4 experiments. Unmetabolized LTE4 was the major radioactive component in the first urine collection, but at later times two more polar compounds predominated. After extensive purification by normal phase-solid phase extraction and reverse-phase high performance liquid chromatography, these compounds were characterized by UV spectroscopy, co-elution with synthetic standards, negative ion electron capture gas chromatography/mass spectrometry, and tandem mass spectrometry. The two major urinary metabolites were structurally determined to be 14-carboxy-hexanor-LTE3 and the conjugated tetraene, 16-carboxy-delta 13-tetranor-LTE4. Three other minor metabolites were detectable in the first urine collection only and were characterized by co-elution with synthetic standards as 16-carboxy-tetranor-LTE3, 18-carboxy-dinor-LTE4, and 20-carboxy-LTE4. omega-Oxidation and subsequent beta-oxidation from the methyl terminus appeared to be the major metabolic fate for sulfidopeptide leukotrienes in man. The accumulation of the 14-COOH-LTE3 and 16-COOH-delta 13-LTE4 may reflect a rate-limiting step in further oxidation of these compounds which places a conjugated triene or conjugated tetraene, respectively, two carbons removed from the CoA ester moiety. Also in the first urine collection there was another minor metabolite identified as N-acetyl-LTE4, however, no subsequent beta-oxidation of this metabolite was observed. The major metabolites of LTE4 might be useful in assessing in vivo production of sulfidopeptide leukotrienes in humans.     

Foetal vascular responses to thromboxane receptor blockade

We hypothesized that foetal administration of SQ-29,548, a putative thromboxane receptor blocker, would prevent foeto-placental vasoconstriction produced by the thromboxane mimic U46619. Arterial blood gases, continuous monitoring of maternal and foetal heart rates and blood pressures were performed in chronically catheterized pregnant ewes. Foetal blood flows and vascular resistance were determined with radioactive microspheres. SQ-29,548 effectively blocked the expected vasoconstrictive effects of thromboxane. However, prolonged infusion of SQ-29,548 resulted in significant decreases in umbilical-placental blood flow and foetal mean arterial pressure. This was accompanied by a respiratory acidemia. Potential therapy for the vasoconstrictive disorders of pregnancy with SQ-29,548 awaits further investigation of its intrinsic vasoactive properties in the umbilical-placental vasculature.     

Leukotriene E4 causes pulmonary vasoconstriction, not inhibited by meclofenamate

Leukotriene E4 (LTE4) appears to be a rather stable product of the lipoxygenase pathway. Its action in the pulmonary circulation is unknown. Therefore we investigated its effect on the circulation of isolated rat lungs perfused with a cell- and plasma-free solution. Synthetic LTE4 in doses from .15 micrograms to 5 micrograms/.25 ml .9% NaCl injected as a bolus in the pulmonary artery during normoxia caused a fast, transient perfusion pressure increase within seconds. This was followed by a slow rise in baseline perfusion pressure (normoxia) over 25 min. In addition, 5 micrograms LTE4 caused edematogenic lung damage. Injection of 1.5 micrograms LTE4 during hypoxic vasoconstriction caused fast, transient pressure rises, similar to normoxic conditions. 6-keto-PGF1 alpha and TXB2 were measured in the lung effluent before and after LTE4 injection. Neither 6-keto-PGF1 alpha nor TXB2 production changed after LTE4 injection. Meclofenamate (.5 micrograms/ml) increased the fast, transient and the slow, sustained pressure rise. We conclude that LTE4 caused direct pulmonary vasoconstriction unrelated to cyclooxygenase products.     

Leukotriene E4 activates peroxisome proliferator-activated receptor gamma and induces prostaglandin D2 generation by human mast cells

Cysteinyl leukotrienes (cys-LTs) are potent inflammatory lipid mediators, of which leukotriene (LT) E(4) is the most stable and abundant in vivo. Although only a weak agonist of established G protein-coupled receptors (GPCRs) for cys-LTs, LTE(4) potentiates airway hyper-responsiveness (AHR) by a cyclooxygenase (COX)-dependent mechanism and induces bronchial eosinophilia. We now report that LTE(4) activates human mast cells (MCs) by a pathway involving cooperation between an MK571-sensitive GPCR and peroxisome proliferator-activated receptor (PPAR)gamma, a nuclear receptor for dietary lipids. Although LTD(4) is more potent than LTE(4) for inducing calcium flux by the human MC sarcoma line LAD2, LTE(4) is more potent for inducing proliferation and chemokine generation, and is at least as potent for upregulating COX-2 expression and causing prostaglandin D(2) (PGD(2)) generation. LTE(4) caused phosphorylation of extracellular signal-regulated kinase (ERK), p90RSK, and cyclic AMP-regulated-binding protein (CREB). ERK activation in response to LTE(4), but not to LTD(4), was resistant to inhibitors of phosphoinositol 3-kinase. LTE(4)-mediated COX-2 induction, PGD(2) generation, and ERK phosphorylation were all sensitive to interference by the PPARgamma antagonist GW9662 and to targeted knockdown of PPARgamma. Although LTE(4)-mediated PGD(2) production was also sensitive to MK571, an antagonist for the type 1 receptor for cys-LTs (CysLT(1)R), it was resistant to knockdown of this receptor. This LTE(4)-selective receptor-mediated pathway may explain the unique physiologic responses of human airways to LTE(4) in vivo.     

Metabolism of leukotriene E4 in isolated rat hepatocytes. Identification of beta-oxidation products of sulfidopeptide leukotrienes

Little is known about the metabolic fate of the sulfidopeptide leukotrienes (LTC4/D4/E4). Earlier studies using radiolabeled leukotrienes have shown that these potent molecules are concentrated and metabolized in the liver when administered to mice and that isolated rat hepatocytes have a high affinity uptake system for LTE4. N-Acetyl-LTE4 has been identified as a metabolite of LTC4 in the bile of rats, but the majority of the metabolites in these studies were not characterized. Based on these earlier reports, incubation of LTE4 with isolated rat hepatocytes was chosen as a model for the study of sulfidopeptide leukotriene metabolism. [3H]LTE4 was incubated with isolated rat hepatocytes and the metabolites formed were purified extensively by ODS flash column chromatography, TLC, and reverse phase-high pressure liquid chromatography. Metabolites were identified by retention of the radiolabel and UV absorbance at 280 nm. Purified metabolites were characterized by UV spectroscopy, fast atom bombardment mass spectrometry, negative ion chemical ionization gas chromatography-mass spectrometry, and electron impact gas chromatography-mass spectrometry. Six LTE4 hepatocyte metabolites were characterized. Metabolite A was determined to be N-acetyl-LTE4. Metabolite B was determined to be the omega-oxidation product 20-carboxy-N-acetyl-LTE4. Metabolite C was characterized as the beta-oxidation product 18-carboxydinor-N-acetyl-LTE4. A further round of beta-oxidation with a concomitant double bond reduction produced Metabolite D, identified as 16-carboxytetranordihydro-N-acetyl-LTE4. The reduction of the 14-15 double bond was most likely the result of the action of 2,4-dienoyl-CoA reductase. The UV spectrum of Metabolite E indicated the presence of a conjugated tetraene, and this metabolite was determined to be 16-carboxytetranor-delta 13-N-acetyl-LTE4. Metabolite F was identified as 14-carboxyhexanor-N-acetyl-LTE4. The observed pathway of beta-oxidation of LTE4 proceeded entirely from the C-20 methyl terminus after omega-oxidation which is in contrast to the known metabolic fate of other eicosanoids. This may be due to the failure to generate the required thioester at C-1 in LTE4 through a strong interaction of the C-5 hydroxy group with the C-1 carboxyl.     

Anaphylactic reaction to penicillin O

Although normally the sympathetic nerves aid vascular dilatation during effort, in certain diseases of the vascular system they have a reverse effect. Abolition of sympathetic vasoconstrictive impulses by sympathectomy is the most effective treatment in some chronic peripheral vascular conditions. The authors have used electrocoagulation for a number of years and found it quick, effective and more likely to prevent regeneration of the affected nerves. Improvement was obtained by sympathectomy in arteriosclerotic vascular insufficiency, thromboangiitis obliterans, Raynaud's disease, reflex sympathetic dystrophy following thrombophlebitis or trauma, scleroderma, spinal sympathetic dystrophy and acquired megacolon. A case of causalgia was aggravated by the operation. Abstention from the use of tobacco appears to be sufficient for control of symptoms in many cases. Since vasospasm is manifested in many conditions long before a thrombotic catastrophe occurs, not only relief of symptoms but prevention of irreversible changes may be achieved by early operation.     

Specificity of receptors for leukotrienes A4, B4, C4, D4, E4 and histamine on the guinea-pig lung parenchyma. Effect of FPL-55712 and desensitization of the myotropic activity

The novel metabolites of arachidonic acid, leukotriene (LT) A4, B4, C4, D4 and E4 have potent myotropic activity on guinea-pig lung parenchymal strip in vitro. The receptors responsible for their action were characterized using desensitization experiments and the selective SRS-A antagonist, FPL-55712. During the continuous infusion of LTB4, the tissues became desensitized to LTB4 but were still responsive to histamine, LTA4, LTC4, LTD4 and LTE4. When LTD4 was infused continuously, the lung strips contracted to LTB4 and histamine but were no longer responsive to LTA4, LTC4, LTD4 and LTE4. Furthermore, FPL-55712 (10 ng ml-1 - 10 ug ml-1) produced dose-dependent inhibitions of LTA4, LTC4, LTD4 and LTE4 without inhibiting the contraction to LTB4 and histamine. On the basis of these results, it appears that the guinea-pig lung parenchyma may have one type of receptor for LTB4 and another for LTD4; LTA4, LTC4 and LTE4 probably act on the LTD4 receptor.     

Radioimmunoassay for leukotriene E4. Use for determination of total sulfidopeptide-leukotriene release from rat gastric mucosa

A conjugate of leukotriene (LT) E4 and bovine serum albumin (BSA) was prepared by covalently linking the free amino group of the hapten to the protein using dimethyl pimelindiimidate (DMP) as coupling reagent. Anti-LTE4 antibodies were raised in rabbits immunized with the conjugate. Binding of [3H]LTE4 to the antibodies is inhibited by 50% with 0.63 ng LTE4, while the relative cross-reaction of LTC4 and LTD4 is 46.3% and 12.6%, respectively. Using the radioimmunoassay release of sulfidopeptide-LT (SP-LT) from rat gastric mucosa incubated in vitro was determined after quantitative enzymatic conversion of SP-LT to LTE4. It could be demonstrated that this method is suitable for determination of SP-LT in biological material.     

Mechanisms of leukotriene E4 partial agonist activity at leukotriene D4 receptors in differentiated U-937 cells

Leukotriene E4 (LTE4) is shown to be a partial agonist of leukotriene D4 (LTD4) in differentiated U-937 cells. The data that support this conclusion are: 1) LTE4 completely displaced [3H]LTD4 from its receptors in U-937 cell membranes. 2) LTE4 induced only 30 +/- 4% of the maximal Ca2+ transient induced by LTD4 in the presence of 1 mM extracellular Ca2+ and 60 +/- 4% of the maximal LTD4 response in the absence of extracellular Ca2+. 3) LTE4 induced only a fraction of the inositol phosphates metabolized by LTD4. Moreover, LTE4 resulted in essentially no production of the inositol 1,4,5-trisphosphate isomer, while LTD4 induced a rapid and substantial transient increase in this isomer. The generation of inositol phosphates by both agonists was unaffected by extracellular Ca2+. 4) The EC50 values for Ca2+ mobilization for LTD4 and LTE4 corresponded with their affinity (Kd values) for the LTD4 receptor. 5) A series of structurally diverse LTD4 receptor antagonists blocked the Ca2+ mobilization responses to LTD4 and LTE4 with identical rank orders of potency. 6) LTE4 acted as an antagonist of LTD4 of potency. 6) LTE4 acted as an antagonist of LTD4 effects when they were coadministered. 7) LTE4 and LTD4 acutely desensitized Ca2+ mobilization to each other. All of the effects of LTE4 are explained by its partial agonist activity at the LTD4 receptor as shown by the following data. 1) Neither LTD4 nor LTE4 had any effect on the agonist activity of fMet-Leu-Phe, LTB4, or platelet-activating factor. 2) None of the above agonists or antagonists to the above receptors affected any of the activities of LTD4 or LTE4. 3) Neither LTD4 nor LTE4 induced desensitization of Ca2+ mobilization to any of the non-LTD4 receptor agonists tested. 4) Under the conditions studied, we have not observed any evidence of multiple subclasses of LTD4 receptors in U-937 cells. LTE4 is a partial agonist of the LTD4 receptor, because it can only couple the LTD4 receptor to a portion of the signaling system available to the receptor when occupied by LTD4. Specifically, LTD4 caused the activation of receptor-operated calcium channels, mobilization of intracellular Ca2+, the activation of phosphatidylinositol-phospholipase C, and the liberation of an additional, as yet undefined, intracellular mediator. To do this, LTD4 receptors couple to at least two and perhaps more guanine nucleotide binding proteins. LTE4 is unable to activate the phosphatidylinositol-phospholipase C but can mimic the other effects of LTD4.(ABSTRACT TRUNCATED AT 400 WORDS)     

Measurement of sulfidopeptide leukotrienes and their metabolism in human synovial fluid of patients with rheumatoid arthritis

Leukotriene (LT)C4 in the synovial fluid of patients with osteoarthritis deformans (OA) and rheumatoid arthritis (RA) was measured by radioimmunoassay (RIA) after extraction with Sep-Pak C18 cartridge. The amounts of immunoreactive LTC4 (i-LTC4) in samples from patients with OA and RA were not significantly different, being 0.198 +/- 0.018 pmol/ml (n = 11) and 0.179 +/- 0.016 pmol/ml (n = 12), respectively. After separation by high performance liquid chromatography (HPLC) and measurement by RIA, the levels of other sulfidopeptide LTs, such as LTD4 and LTE4, in synovial fluid from patients with RA were found to be significantly higher than those in fluid from patients with OA. The leukocyte number in synovial fluids did not correlate with the i-LTC4 level. The metabolic activities of these synovial fluids were determined by incubating them with 3H-LTC4 and then separating sulfidopeptide LTs by HPLC. The conversion of LTC4 to LTD4 in synovial fluids of patients with OA and RA were similar, but the dipeptidase activity converting LTD4 to LTE4 was higher in fluid from patients with RA. It is suggested that a high level of LTE4 may contribute to exudation of synovial fluid, since LTE4 increases vascular permeability.     

The extraction of leukotrienes (LTC4, LTD4, and LTE4) from tissue fluids: the metabolism of these mediators during IgE-dependent hypersensitivity reactions in lung

The metabolites of arachidonic acid known as the leukotrienes are a class of lipid mediators which have potent and diverse biological effects in pulmonary tissue. Leukotrienes C, D, and E (LTC4, LTD4, and LTE4) are known to be principal mediators of immunoglobulin E (IgE)-mediated hypersensitivity reactions in lung tissue. It is therefore important to develop reliable and quantitative isolation techniques for estimating levels of these mediators in tissue. In this study, LTC4, LTD4, and LTE4 were separated from other arachidonate metabolites by organic extraction procedures. 5-Hydroxyeicosatetraeonic acid and leukotriene B4 extract efficiently into the organic layer of aqueous:ether or aqueous:chloroform extractions, whereas arachidonate metabolites containing conjugated peptides (e.g., LTC4, LTD4, and LTE4) failed to extract into these organic solvents. An extraction step was therefore developed that affords quantitative extraction of LTC4, LTD4, and LTE4 into the organic phase of an isopropanol:ether:H2O mixture. This step is the key for a two-step extraction method that isolates histamine, LTC4, LTD4, and LTE4 with a recovery of 100, 85, 75, and 57%, respectively. One advantage of this separation procedure for obtaining these mediators by organic extraction is an ability to expediently process many samples. Furthermore, the leukotriene content of extracted samples can be analyzed using the guinea pig ileum bioassay without interference from vasoamines or platelet-activating factor. These later substances are eliminated from leukotriene-enriched fractions by this extraction process. When histamine and LTC4 were added to supernatant fluids recovered from isolated lung tissue, they were quantitatively recovered using this extraction method.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anaphylactic Reaction to Penicillin O

Although normally the sympathetic nerves aid vascular dilatation during effort, in certain diseases of the vascular system they have a reverse effect. Abolition of sympathetic vasoconstrictive impulses by sympathectomy is the most effective treatment in some chronic peripheral vascular conditions. The authors have used electrocoagulation for a number of years and found it quick, effective and more likely to prevent regeneration of the affected nerves.Improvement was obtained by sympathectomy in arteriosclerotic vascular insufficiency, thromboangiitis obliterans, Raynaud''s disease, reflex sympathetic dystrophy following thrombophlebitis or trauma, scleroderma, spinal sympathetic dystrophy and acquired megacolon. A case of causalgia was aggravated by the operation.Abstention from the use of tobacco appears to be sufficient for control of symptoms in many cases.Since vasospasm is manifested in many conditions long before a thrombotic catastrophe occurs, not only relief of symptoms but prevention of irreversible changes may be achieved by early operation.     

In vivo formation of leukotriene E5 by murine peritoneal cells

Resident mouse peritoneal cells, stimulated in vivo with opsonized zymosan, produced leukotriene C4 and E4, with LTE4 being the major (80-90%) product. When mice were placed on diets containing increasing amounts of fish oil, four additional sulfidopeptide leukotrienes (SP-LT), LTC5, LTE5, 11-trans LTC5 and 11-trans LTE5, were identified. The identity of LTE5 was confirmed by spectrophotometric, chromatographic and enzymatic methods. When equivalent amounts of n-6 and n-3 polyunsaturated fatty acids (PUFA) were included in the diet, the stimulated peritoneal cells (in vivo) produced higher quantities of LTE5 (30.2 +/- 5.4 ng/10(6) cells) than LTE4 (22.8 +/- 7.3 ng/10(6) cells). In addition, in vitro studies demonstrated a 60% reduction in LTC4 (42.0 +/- 10.8 ng/10(6) cells to 16.7 +/- 6.2 ng/10(6) cells) and the appearance of LTC5 (2.1 +/- 0.9 ng/10(6) cells) in resident macrophages (stimulated with A23187) from mice maintained on a fish oil diet compared to mice fed the control diet. This study demonstrated that formation of the pentaenyl SP-LT in vivo, in particular LTE5, by peritoneal cells can significantly contribute to the endogenous SP-LT pool in response to an inflammatory stimulus following a dietary regimen containing fish oil.     

Difference in urinary LTE4 and 11-dehydro-TXB2 excretion in asthmatic patients

Bronchoconstrictor cysteinyl leukotrienes (LT) and thromboxane (TX) A2 have been implicated in the pathogenesis of asthma. Determination of urinary leukotriene E4 (LTE4) and 11-dehydro-TXB2 levels are often used to assess cysteinyl LT and TXA2 production in humans. To define the potential role in the pathogenesis of asthma, we investigated the urinary LTE4 and 11-dehydro-TXB2 levels. LTE4 and 11-dehydro-TXB2 levels were determined using liquid chromatography/tandem mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS), respectively. Urinary LTE4 levels in asthmatic patients (192 +/- 122 pg/mg creatinine, n = 14) were significantly higher (P < 0.005) than those in healthy volunteers (55 +/- 16 pg/mg creatinine, n = 13), but no significant difference in 11-dehydro-TXB2 levels was observed. A significant inverse correlation (r = -0.821, P < 0.005) was found between urinary LTE4 levels and the forced expiratory volume in 1 s (FEV1) but no significant correlation was observed between urinary 11-dehydro-TXB2 levels and FEV1. The present findings suggest that cysteinyl LTs play a more important role in the pathogenesis of asthma than TXA2.     

Inhibition of leukotriene omega-oxidation by omega-trifluoro analogs of leukotrienes

omega-Oxidation with subsequent beta-oxidation from the omega-end is the major pathway for inactivation and degradation of leukotrienes. Oxidative degradation of leukotriene E4 (LTE4), N-acetyl-LTE4, and LTB4 was inhibited by the omega-trifluoro analogs of LTE4, omega-trifluoro-LTE4 (omega-F3-LTE4), and (1S,2R)-5-(3-[1-hydroxy-15,15,15-trifluoro-2-(2-1H- tetrazol-5-ylethyl-thio)pentadeca-3(E),5(Z)-dienyl+ ++]phenyl)-1H-tetrazole (LY 245769). The latter substance inhibited the oxidative degradation of LTE4 and N-acetyl-LTE4 in the rat in vivo by 50% at a dose of 7 mumol/kg body weight. In rat hepatocyte cultures both omega-trifluoro analogs interfered with the omega-oxidation of N-acetyl-LTE4 and LTB4 with IC50 values of about 4 microM. Both analogs inhibited the omega-hydroxylation in isolated rat liver microsomes with IC50 values between 16 and 37 microM. This inhibition is apparently competitive. In addition, in liver cytosol, the conversion of the omega-hydroxylated leukotrienes to omega-carboxy-LTE4 and omega-carboxy-LTB4 was inhibited by both compounds. omega-Trifluoro analogs of leukotrienes provide a new tool for interfering with the inactivation of leukotrienes in the omega-oxidation pathway.