2-methyl-3-(4-(3-pyridinylmethyl)phenyl)-2-propenoic-acid and imidazole

Thromboxane (Tx) inhibition prevents pulmonary leukostasis after acid aspiration. This observation prompted study of polymorphonuclear leukocyte (PMN) accumulations and products of cyclooxygenase. Experiments were conducted with a skin abrasion preparation. Five groups of six rabbits were pretreated intravenously with: (1) placebo, (2) ibuprofen, (3) imidazole and two other Tx syntase inhibitors, (4) OKY 1555, or (5) OKY 046. Zymosan-activated serum (ZAS) and leukotriene B4 were used as chemotaxins and balanced salt solution as control. After pretreatment with placebo, PMN accumulation in leukotriene B4 sites was 2130 +/- 874 PMN/mm3 (mean +/- SD). Pretreatment with ibuprofen, imidazole, or OKY 046 decreased (p less than 0.05) accumulations to 205 +/- 139 PMN/mm3, 485 +/- 387 PMN/mm3, and 504 +/- 260 PMN/mm3, respectively. In ZAS sites, placebo pretreatment led to 2006 +/- 866 PMN/mm3, while the ibuprofen, imidazole, and OKY 046 groups had decreased (p less than 0.05) responses of 295 +/- 218 PMN/mm3, 444 +/- 477 PMN/mm3, and 386 +/- 151 PMN/mm3, respectively. Pretreatment with OKY 1555 did not produce significant reductions in response. Six animals in each group received intradermal injections of the two chemotaxins or Hank's balanced salt solution. Reduction in PMN accumulations after cyclooxygenase and Tx inhibition were similar to those observed in the skin abrasion preparation. Pretreatment with either ibuprofen, imidazole, or OKY 046 resulted in a decreased concentration of Tx in abrasion fluid exudate in response to leukotriene B4, 275 +/- 164 pg/ml, 460 +/- 144 pg/ml, and 440 +/- 260 pg/ml, respectively, as compared with 1168 +/- 380 pg/ml in the placebo group. The reduced responses were not the result of a decrease in regional perfusion as measured by 133Xe washout. The in vitro chemotactic response of PMN to leukotriene B4 and ZAS was unchanged after incubation in either ibuprofen, imidazole, OKY 1555, or OKY 046. These data show that cyclooxygenase and Tx syntase are integrally associated with PMN accumulations.

Topics: Animals; Chemotaxis, Leukocyte; Cyclooxygenase Inhibitors; Ibuprofen; Imidazoles; Male; Methacrylates; Neutrophils; Premedication; Prostaglandin-Endoperoxide Synthases; Rabbits; Skin; Skin Tests; Thromboxane A2; Thromboxane-A Synthase

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

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 potential role of thromboxane (TxA2), a platelet aggregator and vasoconstrictor, and prostacyclin (PGI2) a platelet anti-aggregator and vasodilator, in endotoxic and septic shock was investigated. Early endotoxic shock in the rat is associated with marked elevations of plasma TxB2 (the stable metabolite of TxA2) and lesser increases in plasma 6-keto-PGF1 alpha (the stable metabolite of PGI2). Selective inhibition of TxA2 synthesis by several different chemical classes of Tx synthetase inhibitors was beneficial in endotoxic shock. In contrast, shock induced by acute intra-abdominal sepsis in the rat was characterized by high levels of plasma 6-keto-PGF1 alpha, which exceeded plasma TxA2 six- to eight fold at most time intervals studied. Tx synthetase inhibitors were not protective in this model of acute sepsis, but treatment with fatty acid cyclo-oxygenase inhibitors, an antibiotic (gentamicin), or reduction in arachidonic acid metabolism by essential fatty acid (EFA) deficiency significantly prolonged survival time. An important aspect of the latter study is that decreased arachidonic acid metabolism was an effective adjunct to antibiotic therapy. Conjoint administration of gentamicin in EFA-deficient rats or with indomethacin synergistically improved long-term survival, a result that was not evident with single treatment interventions. In addition to experimental studies, plasma TxB2 levels were measured during clinical sepsis. These studies demonstrated that plasma TxB2 levels were elevated tenfold in patients dying of septic shock compared with septic survivors or nonseptic controls. These composite experimental and clinical observations suggest that arachidonic acid metabolites play a role in the pathogenesis of endotoxic and septic shock.

Topics: Animals; Arachidonic Acids; Aspirin; Cyclooxygenase Inhibitors; Epoprostenol; Fatty Acids; Gentamicins; Ibuprofen; Imidazoles; Methacrylates; Peritonitis; Rats; Rats, Inbred Strains; Shock, Septic; Thromboxane-A Synthase; Thromboxanes

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