Inhibition of analgesic-induced asthma by leukotriene receptor antagonist ONO-1078

We evaluated the effect of ONO-1078, a selective leukotriene-C4, -D4, and -E4-receptor antagonist, on bronchoconstriction intensity during inhalation challenge with dipyrone (a pyrazolone derivative) in six aspirin-sensitive asthmatics. A double-blind, randomized, crossover design was used. After ingestion of 225 mg ONO-1078 or matching placebo, subjects underwent bronchial provocation with dipyrone on two occasions, separated by 4 wk. Aerosol inhalation of dipyrone was performed increasing the concentration stepwise from 0.08 to 10% (wt/vol). FEV1 was measured every 10 min up to 30 min after inhalation of each concentration. Threshold concentrations causing a fall in FEV1 > or = 20% of baseline value were 0.4% in four subjects and 2% in the other two on the placebo day. After pretreatment with ONO-1078, threshold concentration was 10% in two subjects, and no fall in FEV1 was observed in the other four, even after inhalation of 10% dipyrone. Values of PD20 were 21.9 +/- 8.2 units (mean +/- SEM) after placebo and 311.6 +/- 40.3 units after ONO-1078, respectively, and a statistically significant difference occurred (p < 0.001). Provocation of bronchoconstriction was completely inhibited in subjects whose plasma ONO-1078 levels were more than 0.5 microgram/ml. These results support the hypothesis that sulfidopeptide leukotriene-induced bronchoconstriction is one important component in the pathophysiology of aspirin-induced asthma.

Reduction of the severity of bronchial hyperresponsiveness by the novel leukotriene antagonist 4-oxo-8-[4-(4-phenyl-butoxy)benzoylamino]-2- (tetrazol-5-yl)-4H-1-benzopyran hemihydrate

There is much evidence that the cysteinyl-leukotrienes (C-LTs) are important in the pathogenesis of asthma. The clinical effect of a new leukotriene antagonist, ONO 1078 (4-oxo-8-[4-phenylbutoxy)benzoylamino]-2-(tetrazol-5-yl)-4H- 1-benzopyran hemihydrate, CAS 103177-37-3) on symptoms, pulmonary lung function and bronchial hyperresponsiveness was evaluated in patients with bronchial asthma. Eleven patients were treated for 24 weeks with 450 mg of ONO 1078 twice daily. The score of asthma symptom severity and the number of inhaled procaterol were significantly reduced after 2 weeks of ONO 1078 treatment and remained decreased for another 22 weeks. Their FEV1 and PC20 to histamine significantly improved 12 and 24 weeks after ONO 1078 treatment. The effectiveness of ONO 1078 suggests that the C-LTs play an important role in the pathogenesis of asthma. ONO 1078 might help to favorably modify the pathophysiologic condition in patients with bronchial asthma.

Synthesis of epoxypropyloxy chromones and allyl hydroxy chromones and in vitro-in vivo activity on protoscoleces of Echinococcus multilocularis (Cestoda)

Derivatives with epoxypropyloxy, allyloxy and allyl hydroxychromone structures were synthesized and tested against protoscoleces of Echinococcus multilocularis. Compounds IV-IX were tested in vitro and compound VII proved the most active of them with, at 0.1 mmol.L-1, 98% dead protoscoleces in open vesicles after 24 hours and 80% in closed vesicles within 96 hours. Compound VII was tested in vivo on Meriones unguiculatus infested by Echinococcus multilocularis, but was found to be rather inactive.

The effects of a cysteinyl leukotriene antagonist (ONO-1078) on antigen-induced responses in allergic sheep

The cysteinyl leukotrienes (LTC4/D4/E4) are putative mediators of asthma. In this study we used sheep allergic to Ascaris suum antigen to examine the effects of a novel orally active cysteinyl LT antagonist, ONO-1078, on antigen-induced early and late responses, airway inflammation, post challenge (24 h) airway hyperresponsiveness (AHR) and mucociliary clearance. Airway responses to antigen were determined by measuring specific lung resistance (SRL) before and for 8 h after challenge, bronchoalveolar lavage (BAL) was used to estimate airway inflammation, and airway responsiveness was measured by determining the carbachol dose that increased SRL by 400% (PC400). We also used a radiographic technique to measure the antigen-induced change in tracheal mucus velocity (TMV), a marker of mucociliary clearance. In two trials separated by at least 21 days, sheep were treated once with ONO-1078 (30 mg/kg, p.o.) and once with placebo (0.5% methylcellulose), 2 h before and 4 h after antigen challenge. Treatment with ONO-1078 (n = 7) provided 40% protection (p < 0.10) against the peak early increase in SRL, resulted in a more rapid reversal of the early response, and provided 96% protection against the peak late (6-8 h) increase in SRL. ONO-1078 also inhibited the AHR 24 h after challenge. In the drug trial, PC400 was unchanged as compared to pre-challenge, whereas in the placebo trial, PC400 was decreased 1.4-fold (p < 0.05). Treatment however, did not affect BAL cell numbers or differential.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a leukotriene antagonist, ONO-1078, on bronchial hyperresponsiveness in patients with asthma

To evaluate the involvement of sulphidopeptide leukotrienes on bronchial hyperresponsiveness in asthma, we examined the effects of a specific orally active leukotriene antagonist (ONO-1078) on bronchial responsiveness to methacholine in stable asthmatic subjects by a double-blinded, randomized, two-phase crossover study. Eleven asthmatic subjects received ONO-1078 (225 mg twice a day) or placebo. After 1 week administration of ONO-1078 or placebo, the subjects underwent methacholine challenge test. Test drug administrations were then discontinued for 1 week, and the subjects were then crossed over to the alternative treatment regimen. After 1 week of the alternate regimen, the subjects underwent a second methacholine challenge. Mean baseline values of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) and geometric mean value of provocative concentration of methacholine causing a 20% fall in FEV1 (PC20-FEV1) were equal between the first and the second methacholine test. The geometric mean value of PC20-FEV1 after the administration of ONO-1078 was 0.48 (geometric SEM, 1.48) mg ml-1, which was significantly (P < 0.01) greater than the value after the placebo administration (0.30 geometric SEM, 1.41 mg ml-1), but the baseline values of FVC and FEV1 were not altered by ONO-1078. We conclude that sulphidopeptide leukotrienes are significantly involved in the development of bronchial hyperresponsiveness in asthma but the degree of the involvement may be small.

Antagonists and inhibitors of lipid mediators in experimental inflammation of the cornea

In experimental immunogenic keratitis, provoked in rabbits by intracorneal injection of 20 microliters of human serum albumin (HSA), various anti-inflammatory agents were studied in their effects on corneal edema, neovascularisation and leukocyte infiltration. Prophylactic treatment with a corticosteroid completely prevented the occurrence of keratitis. Nonsteroidal anti-inflammatory drugs such as a cyclooxygenase inhibitor partly prevented neovascularisation and corneal edema, a lipoxygenase inhibitor, a leukotriene antagonist or platelet-activating factor (PAF)-antagonist BN 52021 partially prevented mainly leukocyte infiltration. Prophylactic topical treatment with the poly-unsaturated fatty acids eicosapentaenoic acid and columbinic acid or a dietary supplement with fish oil showed less symptoms of keratitis in all respects.

Effect of platelet-activating factor antagonist and leukotriene antagonist on endotoxin shock in the rat: role of the leukocyte

The effects of platelet-activating factor (PAF) antagonist (CV-3988) and leukotrienes (LTs) antagonist (ONO-1078) on endotoxin-induced sequelae in the rat were assessed. Pretreatment with either CV-3988 (6 mg/kg, i.v.) or ONO-1078 (150 mg/kg, p.o.) did not improve survival rate following the administration of Escherichia coli lipopolysaccharide (LPS) compared with that of control rats pretreated with solvents of the drugs. Rats pretreated with both CV-3988 and ONO-1078 exhibited significantly (P less than 0.01) enhanced survival following lipopolysaccharide (LPS) administration. Percentage survivals 48 hr after the administration of LPS were 20%, 32%, 24%, and 68% in the pretreatment with solvents, CV-3988, ONO-1078, and CV-3988 combined with ONO-1078 groups, respectively. Pretreatment with CV-3988 combined with ONO-1078 inhibited the change of plasma transaminase 3 hr after LPS administration. The neutropenia, due to the administration of vinblastine (1 mg/kg, i.v.), increased the survival rate following the administration of LPS without pretreatment with PAF and LT antagonists. Antishock action of CV-3988 and ONO-1078 could not be seen in neutropenic rats. These data suggest that combined pretreatment with PAF antagonist and LT antagonist inhibited leukocyte-mediated tissue injury in LPS-induced endotoxemia.

Marine bioactive compounds: stereospecific anti-inflammatory activity of natural and synthetic cordiachromene A

A new synthesis is proposed for cordiachromene A (CCA), a bioactive component of the ascidian Aplidium antillense Gravier, using a method producing a racemic mixture. The anti-inflammatory activities of a natural extract and a chemically synthetic form of CCA were assessed in vivo by carrageenan-induced rat-paw edema. The activity of synthetic CCA was confirmed by a test on kaolin-induced granuloma in the rat. Strong activities were measured for both CCA, but comparison of results of the first test suggests that only the natural optically active isomer has an anti-inflammatory effect. CCA is similar to indomethacin in its effect on carrageenan-induced rat-paw edema and ten times as active as phenylbutazone.

Mast cell modulation of tumour cell proliferation in rat mammary adenocarcinoma 13762NF

Mast cells were shown to accumulate around the periphery of the invasive and metastatic rat mammary adenocarcinoma (MTLn3), and histological evidence of mast cell degranulation was observed during the later stages of this model. To assess the physiological role of mast cells in vivo we have used the mast cell-stabilising compound FPL 55618 applied i.p. daily at 1 mg kg-1 for 23 days. Using groups of 12 rats we have found that this compound inhibited tumour growth at the primary site by as much as 70% in most of the treated animals compared with the control group which received equivalent volumes of saline. When the drug treatment was stopped after 23 days, tumour growth of the test group accelerated over the next 7 days and reached a similar tumour size to that of control animals. Histological studies of the tumour and contiguous host tissue at day 24 of the experiment revealed numerous extra-tumoural mast cells often showing signs of degranulation at several sites around the tumour periphery in the control animals. Such observations were not seen in those animals receiving FPL 55618 where, in contrast to controls, numerous intact mast cells were often seen within the tumour mass. Following cessation of the MC-stabilising treatment progressive mast cell activation was evident within 2-4 days, primarily at the tumour periphery. In vitro studies have shown that drug concentrations equivalent to five times the in vivo dose had no effect on the proliferative rate or viability of the MTLn3 cells. Moreover, the proliferative rate of these cells in culture was significantly increased when exposed to soluble mast cell products. Thus our data indicate that a mast cell-stabilising compound has significant benefits in reducing tumour growth in vivo, an observation which supports the concept that mast cell:tumour cell interactions are important for the growth and invasive properties demonstrated by this model of breast carcinoma.

Effects of N-556 on experimental allergy models in rats

The oral anti-allergic effect of 1,3-bis-(2- ethoxycarbonylchromon-5-yloxy)-2-((S)-lysyloxy)propane dihydrochloride (N-556, KY-556) was investigated. 1) N-556 (10-100 mg/kg, p.o.) inhibited dose-dependently the 48-hr homologous PCA in rats, and the duration of action was longer than that of intravenous DSCG. 2) N-556 (20 and 100 mg/kg once a day for 20 consecutive days, p.o.) tended to inhibit the histamine release from actively sensitized rat lung fragments. 3) N-556 (100 mg/kg, p.o.) showed the prolongation of survival time in the rat systemic anaphylaxis. 4) N-556 (100 mg/kg, p.o.) significantly inhibited the increased airway resistance in experimental asthma in rats. These results suggest that N-556 is a promising and orally-active pro-drug of disodium cromoglycate (DSCG) against allergic diseases.

Preventive effect of several drugs against Pseudomonas aeruginosa infection and the toxicity of combined tumor necrosis factor with lipopolysaccharide: relationship between lethality and the arachidonic cascade

The participation of tumor necrosis factor (TNF) and lipopolysaccharide (LPS) in Pseudomonas aeruginosa (Pa) infection was examined. The lethal challenge of Pa or TNF and LPS injection could be prevented by pretreatment with anti-TNF antibody, polymyxin B, ONO 1078, or Shosaiko-to. The combined effects of TNF and LPS may be deeply related to the lethality of Pa infection. The activities of leukotriene(LT) C4/D4/E4 or platelet activating factor (PAF) were also related to the lethality of Pa infection, probably due to the subsequently produced TNF which acts in combination with LPS. Activating the host defence mechanism with biological response modifiers like Chinese medicines was effective against Pa infection. One mechanism could involve an activity as an LT inhibitor or PAF antagonist. Following the administration of TNF and/or LPS, the serum levels of arachidonic cascade products underwent various changes. With a combination of TNF and LPS, there was a synergistic increment of prostaglandins, thromboxane, and LT. Following pretreatment with Shosaiko-to, suppression of LTs was dominant even with the combination of TNF and LPS, which might be related to the lethality of the infection or combined TNF with LPS.

Leukotriene-receptor antagonist FPL-55712 and t-PA-induced thrombolysis in canine coronary thrombosis

Leukocyte-derived arachidonate products peptido-leukotrienes have been shown to induce coronary constriction and platelet aggregation. As such, leukocytes may have a role in coronary thrombosis and coronary re-occlusion following thrombolysis. In the present study, we examined the effects of tissue-plasminogen activator (t-PA, 0.75 mg/kg over 20 minutes) given after either saline or FPL-55712 (2 mg/kg), a peptido-leukotriene receptor antagonist, in dogs with electrically-induced coronary thrombosis. Peripheral blood neutrophil number and superoxide anion generation increased (P less than 0.01) during formation of thrombus and subsequent t-PA administration in saline-treated dogs. FPL-55712 pretreatment attenuated (P less than 0.05) the increase in number of and superoxide anion generation by neutrophils. However, frequency of thrombolysis, duration of restored flow and re-occlusion rates were similar (P-NS) in both groups of dogs. This study shows that FPL-55712 does not modulate the thrombolytic potential of t-PA even though it decreases neutrophil activation in response to myocardial ischemia.

[Effect of KP-136 on allergic paw edema in the rat]

The pharmacological properties of KP-136, an inhibitor of type I allergy, were studied in rat paw models. In four allergic responses, three of the immediate type and one delayed type, KP-136 (p.o.) produced potent inhibitions on the mast cell-mediated type I allergy (ID30: 1.0 mg/kg) and the neutrophil-infiltrated passive Arthus reaction (ID30: 1.6 mg/kg). In addition, KP-136 (10 mg/kg, 50 mg/kg, p.o.) inhibited the injury of bone tissues in rat adjuvant arthritis, confirming that it was effective on the allergic inflammation with tissue injury. Although KP-136 was a weak inhibitor of carrageenin-induced paw edema, prostaglandin synthesis and complement-mediated hemolysis, the compound inhibited the release of lysosomal enzymes such as lysozyme and beta-glucuronidase in the passive Arthus reaction, suggesting the blockage of inflammatory mediator release for its mode of action.

Inhibition of endogenous leukotriene-mediated lung anaphylaxis in guinea pigs by a novel receptor antagonist ONO-1078

The inhibitory effect of ONO-1078, a novel leukotriene (LT) receptor antagonist, was investigated on guinea pig lung anaphylaxis in vitro and in vivo. It was demonstrated that this compound could inhibit the late phase of contractile responses in Schultz-Dale reactions and endogenous LT-mediated bronchoconstrictions in passively sensitized guinea pigs, in a dose-dependent fashion, implying its clinical usefulness in the treatment of human bronchial asthma.

Protective effects of a thromboxane synthetase inhibitor, a thromboxane antagonist, a lipoxygenase inhibitor and a leukotriene C4, D4 antagonist on myocardial injury caused by acute myocardial infarction in the canine heart

We studied the effects of a thromboxane A2 synthetase inhibitor (RS-5186), a thromboxane A2 antagonist (ONO-3708), a 5-lipoxygenase inhibitor (AA-861) and a peptidoleukotriene antagonist (ONO-1078) on infarct size, polymorphonuclear leukocyte infiltration, gross myocardial hemorrhage and arrhythmias in the canine coronary occlusion (2 hour)-reperfusion model (5 hour). The infarct size and risk area were determined by a double staining technique. Thirty minutes prior to occluding the coronary arteries, dogs were randomly assigned to one of the following five groups: the thromboxane A2 synthetase inhibitor group (n = 11) receiving RS-5186 10 mg/kg i.v., the thromboxane A2 antagonist group (n = 12) receiving continuous intravenous infusion of ONO-3708 1 microgram/kg/min, the lipoxygenase inhibitor group (n = 11) receiving AA-861 3 mg/kg i.v., the peptidoleukotriene antagonist group (n = 11) receiving continuous intravenous infusion of ONO-1078 1 microgram/kg/min and the vehicle control group (n = 15). Except for ONO-3708, all the other drugs reduced the infarct size (RS-5186: 26.3 +/- 2.4% of risk area (mean +/- SEM), AA-861: 21.8 +/- 1.3%, ONO-1078: 22.5 +/- 4.4% vs control: 54.0 +/- 6.4%, p less than 0.01 respectively) as well as reducing the area of gross myocardial hemorrhage (RS-5186: 3.9 +/- 2.6% of infarct size, AA-861: 5.1 +/- 2.4%, ONO-1078: 5.2 +/- 2.5% vs control: 22.3 +/- 3.9%, p less than 0.01 respectively). RS-5186 and AA-861 reduced the intensity of polymorphonuclear leukocyte infiltration into the infarcted area, however, neither ONO-3708 nor ONO-1078 had any significant influence.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of traxanox sodium on blood pressure and serum uric acid in hypertensive patients: a preliminary study

The effects of chronic administration of traxanox sodium (traxanox) on blood pressure and serum uric acid level were investigated in 15 patients who had mild to moderate hypertension. Traxanox or its placebo was orally administered in a single-blind protocol. Blood pressure was significantly reduced from baseline after treatment with traxanox. The serum uric acid level after drug administration was significantly lower than with placebo whereas urinary uric acid excretion was significantly greater and uric acid clearance tended to be greater. These results indicate that chronic administration of traxanox reduces serum uric acid level as well as blood pressure in patients with mild to moderate hypertension. This reduction in serum uric acid is due in part to a traxanox-induced elevation of urinary uric acid excretion.

The protective mechanism of FPL55712 against stress-induced gastric ulceration in rats

Cold-restraint stress produced stomach ulceration which was accompanied by a decreased glandular mucosal mast cell count and blood flow. Pretreatment with FPL55712, a leukotriene antagonist, dose-dependently prevented ulcer formation and mast cell depletion; however, it did not affect the reduced mucosal blood flow, nor did it significantly influence acid secretion and pepsin output. The role of the leukotrienes in stress ulceration is discussed in the light of the findings with FPL55712 on gastric glandular mucosal mast cell degranulation.

Effect of 8-hexyloxy-3-(1H-tetrazol-5-yl)-2H-chromen-2-one [KP-136] on experimental asthma: a comparison with disodium cromoglycate

The pharmacological properties of 8-hexyloxy-3-(1H-tetrazol-5-yl)-2H-chromen-2-one, KP-136 were compared with those of an antiallergic medicament, disodium cromoglycate (DSCG) in experimental asthma models. KP-136 (0.125-1 mg/kg i.v., 0.5-2 mg/kg p.o.) produced a dose-dependent inhibition to allergic asthma of rats and was more potent than DSCG (1-5 mg/kg i.v.). KP-136 (1 mg/kg, i.v.) was also effective on allergic asthma of guinea pigs, although DSCG was ineffective even at a high dose of 50 mg/kg (i.v.). In rats, both KP-136 and DSCG significantly blocked the reduction of histamine content of the trachea after allergic asthma and inhibited the antigen-induced histamine release from lung fragments (KP-136 0.5 micrograms/ml, DSCG 50 micrograms/ml) and peritoneal exudate cells (KP-136 0.1 micrograms/ml, DSCG 10 micrograms/ml). KP-136 also showed relaxation activity for isolated guinea pig trachea at high doses of 2 and 5 micrograms/ml. The major mechanism of the potent antiasthmatic activity of KP-136 is postulated to be the blocking of bronchoactive mediator release. The relaxation of smooth muscle is also suggested to be an additive mechanism.

Antigen-induced bronchopulmonary alterations in the guinea pig: a new model of passive sensitization mediated by mouse IgE antibodies

A selective model to study the IgE-mediated anaphylactic bronchoconstriction (BC) in the guinea pig is needed, since human asthma involves mainly this class of antibody. However, most procedures presently available for passive homologous or active sensitization lead to responses which are mediated both by IgE and IgG antibodies. In this study, we developed an anaphylactic model in which guinea pigs are passively sensitized with mouse ascitic fluid containing dinitrophenol (DNP)-specific IgE antibodies. Challenge of sensitized animals with DNP coupled to bovine serum albumin evokes a bronchoconstrictor response that is maximal 5 h after sensitization. The resulting anaphylactic BC is not blocked by the H1 histamine antagonist mepyramine, by the peptido-leukotriene antagonist FLP 55712 nor by the platelet-activating factor antagonist BN 52021 alone. However, when the sensitized animals are pretreated with the three drugs in combination, significantly reduced BC was observed upon challenge with the antigen. This latter result indicates that IgE-dependent BC involves the participation of different mediators, a characteristic shared in common with allergic asthma in human.

[Exercise-induced asthma]

Exercise-induced asthma only differs from common asthma in its causative factor. It is a typical asthmatic attack which follows a strenuous and continuous physical exercise lasting 5 to 10 minutes, most often in cold and dry weather. The prevalence of exercise-induced asthma has not yet been firmly established; its pathophysiological mechanisms are still debated, and the respective roles of heat and water losses by the airways are not clearly defined. However, the influence of the type of exercise as a precipitating factor of exercise-induced asthma is now well-known. All things being equal, swimming generates less asthma than running and cycling. This enables the subjects to be directed towards the most suitable sports and encouraged to improve their physical fitness. Drug treatment of exercise-induced asthma must preferentially be preventive; it relies on cromoglycate and beta-2 adrenergic agonists, the latter being also capable of treating acute exercise-induced bronchial obstruction. Education of the patients and their family is also important.

[Effects of traxanox sodium on experimental nasal allergy]

The anti-allergic actions of traxanox sodium pentahydrate (traxanox) were examined using experimental allergic rhinitis models. Traxanox (10 and 30 mg/kg, p.o.), tranilast (30 and 100 mg/kg, p.o.) and disodium cromoglycate (DSCG, 3 and 10 mg/kg, i.v.) dose-dependently inhibited the increase of dye leakage in rats actively sensitized with dinitrophenol-coupled ascaris extract. Traxanox was about 4 times more potent than tranilast. In this test, the inhibitory activity of traxanox (30 mg/kg, p.o.) was not affected by predosing with the same dose for 7 days. In addition, traxanox (1-10 mg/kg, i.v.) inhibited the allergically induced increase in nasal resistance of guinea pigs actively sensitized with egg albumin, while tranilast (10 mg/kg, i.v.), DSCG (100 mg/kg, i.v.) and mepyramine (1 mg/kg, i.v.) had little effect. These results suggest that traxanox may be clinically effective in treating patients with nasal allergies.

The effects of lipoxygenase inhibitor and peptidoleukotriene antagonist on myocardial injury in a canine coronary occlusion-reperfusion model

We studied effects of lipoxygenase inhibitor (AA-861) and peptidoleukotriene antagonist (ONO-1078) on infarct size, polymorphonuclear leukocyte (PMNs) infiltration, gross myocardial hemorrhage and ventricular arrhythmias in canine coronary occlusion (2 hr)-reperfusion (5 hr) model. Infarct size (IS) and risk area (RA) were determined by dual staining technique. Thirty minutes before coronary occlusion dogs were randomly assigned to one of the following three groups: lipoxygenase inhibitor group (n = 11) receiving AA-861 3 mg/kg i.v., peptidoleukotriene antagonist group (n = 11) receiving continuous intravenous infusion of ONO-1078 1 micrograms/kg/min and vehicle control group (n = 15). Both AA-861 and ONO-1078 reduced infarct size [AA-861: 21.8 +/- 1.3% of RA (mean +/- SEM), ONO-1078: 22.5 +/- 4.4% vs

CONTROL

54.0 +/- 6.4%, p less than 0.01 and p less than 0.01, respectively] and area of gross myocardial hemorrhage (AA-861: 5.1 +/- 2.4% of IS, ONO-1078: 5.2 +/- 2.5% vs

CONTROL

22.3 +/- 3.9%, p less than 0.01 and p less than 0.01, respectively). Both drugs also decreased frequency of ventricular premature contractions both during occlusion and during reperfusion, and that of ventricular tachycardia during reperfusion. AA-861 inhibited PMNs recruitment into infarcted area. However, ONO-1078 had no significant influence on degree of PMNs infiltration. These results suggest that lipoxygenase products, especially peptidoleukotrienes (LTC4, D4 and E4) may play important roles in the pathogenesis of myocardial ischemic and reperfusion injuries.