thromboxane-b2 and nafazatrom

We studied the effect of nafazatrom on plasma prostacyclin (PGI2) levels, platelet function, and thromboxane B2 (TxB2), and 12-hydroxy-eicosatetraenoic acid (12-HETE) production and clinical improvement in 12 patients with peripheral vascular disease (PVD) by means of a double-blind crossover trial of placebo, 800 or 1600 mg of nafazatrom four times daily for 1 week, with intervening 2-week washout periods. Plasma PGI2 levels were measured as 6-keto-PGF1 alpha by radioimmunoassay. Platelet function ex vivo was measured as collagen and adenosine diphosphate (ADP)-induced platelet aggregation, release of 12-HETE and thromboxane A2 (measured as TxB2), and was determined by high-pressure liquid chromatography (HPLC) and radioimmunoassay, respectively. The plasma 6-keto-PGF1 alpha levels were unaffected by nafazatrom treatment (p greater than 0.25). Nafazatrom treatment had no effect on TxB2 production, but significantly altered the production of the platelet 12-HETE (p less than 0.05). There was a significant association between the changes in 12-HETE production and clinical improvement. These results suggest that the mechanism of action of nafazatrom is in part related to the inhibition of platelet function via the lipoxygenase pathway, independent of PGI2 stimulation.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Adult; Aged; Arterial Occlusive Diseases; beta-Thromboglobulin; Blood Platelets; Clinical Trials as Topic; Double-Blind Method; Drug Administration Schedule; Epoprostenol; Humans; Hydroxyeicosatetraenoic Acids; Middle Aged; Platelet Adhesiveness; Platelet Aggregation; Pyrazoles; Pyrazolones; Random Allocation; Thromboxane B2

Nafazatrom (Bay G 6575) is a novel antithrombotic compound, which acts by stimulation of prostacyclin as well as by inhibition of lipoxygenase enzymes. To determine its effects on exercise performance in coronary artery disease patients, a double-blind study was conducted. Twenty patients with coronary artery disease underwent an exercise stress test before and 2 hours after administration of placebo or nafazatrom (1.2 gm). Before the drug administration, there was evidence of enhanced platelet activity, as reflected by elevated resting plasma beta thromboglobulin and thromboxane B2 concentrations. Plasma 6-keto-PGF1 alpha levels were undetectable in most patients. All coagulation tests were in the normal range. None of these parameters changed with exercise. Administration of placebo or nafazatrom before the exercise stress test did not significantly influence any of the coagulation or platelet function parameters or plasma concentrations of thromboxane B2 and 6-keto-PGF1 alpha. This lack of effect was evident both at rest and upon exercise. Compared to placebo, nafazatrom did not significantly increase exercise tolerance time or exercise-induced symptoms. In conclusion, nafazatrom did not influence exercise performance in patients with coronary disease.

Topics: 6-Ketoprostaglandin F1 alpha; beta-Thromboglobulin; Blood Pressure; Coronary Disease; Exercise Test; Female; Fibrinolytic Agents; Heart Rate; Humans; Male; Middle Aged; Platelet Count; Platelet Factor 4; Pyrazoles; Pyrazolones; Thromboxane B2

A sensitive RIA for LTB4 (which cross-reacts 60% with 6-trans LTB4) has been developed with a minimal detectable mass of 7.4 X 10(-15) mole. The properties of a second RIA more specific for 6-trans LTB4 are also described. The latter has utility in the measurement of the enzymatic and non-enzymatic transformations of LTA4 and in the characterisation of inhibitors of LTA4 epoxide hydrolase. Conditions for the direct RIA of immunoreactive LTB4 in human plasma are described. Addition of calcium ionophore, A23187, to human blood increased basal immunoreactive LTB4 levels from less than 100pg ml-1 to 259 +/- 23ng ml-1 (mean +/- SEM, n = 16). Extraction and RPHPLC confirmed that greater than 90% of immunoreactive LTB4 co-eluted with synthetic and [3H]LTB4. Pharmacological characterisation of immunoreactive eicosanoids revealed that in vitro the NSAIDs: aspirin, indomethacin, flurbiprofen and benoxaprofen did not inhibit LTB4 but inhibited TXB2, consistent with cyclo-oxygenase inhibition whereas the prototype mixed inhibitor BW755c inhibited both LTB4 and TXB2. This experimental paradigm may be used in the clinical measurement of the bio-availability of novel agents that inhibit eicosanoid biosynthesis.

Topics: 4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; Animals; Antibodies; Antibody Specificity; Calcimycin; Catechols; Chromatography, High Pressure Liquid; Cross Reactions; Dose-Response Relationship, Drug; Female; Humans; Leukotriene B4; Male; Masoprocol; Pyrazoles; Pyrazolones; Rabbits; Radioimmunoassay; Thromboxane B2; Time Factors

Mice transplanted with NC carcinoma were treated with the thromboxane synthetase inhibitor dazmegrel (UK38485) or with nafazatrom (BAY G 6575), a compound that is reported to increase prostacyclin formation. Some experiments included the cytotoxic drugs methotrexate and melphalan. The tumours were excised under anaesthesia on day 14 or day 21 after transplantation, and weighed; some were extracted for prostanoids which were measured by radioimmunoassay. Mouse survival time was determined up to day 121, and cancer spread was determined by postmortem examination. The survival was increased by methotrexate and melphalan but not by the other drugs. Nafazatrom-treated mice tended to have lighter tumours. Although dazmegrel reduced the formation of thromboxane B2 during clotting of blood from normal mice, it did not affect the tumour yields of prostanoids. Nafazatrom had no effect on serum or tumour prostanoids. There were no obvious effects of the treatments on the recurrence of tumour in the excision scar, lung metastasis or spread to lymph nodes.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Antineoplastic Agents; Female; Imidazoles; Mammary Neoplasms, Experimental; Mice; Prostaglandins E; Pyrazoles; Pyrazolones; Thromboxane B2; Thromboxane-A Synthase

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

Nafazatrom is an antithrombic drug that has been shown to have beneficial effects in traumatic shock and organ ischemia. This study evaluated the effect of nafazatrom on cardiovascular, sympathetic, and endocrine consequences to moderate or severe hemorrhagic shock in the conscious rat. Nafazatrom (2 mg/kg, i.v.) had no effect on the blood pressure, heart rate, and circulatory norepinephrine, vasopressin, and leukotriene C4 responses to bleeding. Nafazatrom significantly reduced plasma TXB2 and 6-keto-PGF1 alpha and blocked the increment in these cyclooxygenase metabolites in response to hemorrhage. It is concluded that nafazatrom does not increase survival after moderate hypovolemic hypotension and decreases survival to severe hemorrhage. Nafazatrom does not modify the cardiovascular, sympathetic, and neuroendocrine responses to hypovolemic hypotension.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Arginine Vasopressin; Blood Pressure; Epinephrine; Fibrinolytic Agents; Heart Rate; Male; Norepinephrine; Pyrazoles; Pyrazolones; Rats; Rats, Inbred Strains; Shock, Hemorrhagic; SRS-A; Thromboxane B2

The effects of lipoxygenase enzyme inhibitor nafazatrom on infarct size, haemodynamics, and prostanoid release was studied in a canine occlusion-reperfusion model of ischaemic myocardial injury. Treatment was with 10 mg/kg nafazatrom i.d., starting before coronary occlusion, 2 h and 6 h thereafter, and was repeated in 6 h intervals. The left anterior descending (LAD) coronary artery was occluded for 6 h and reperfused for 42 h. Infarct size and anatomic area dependent on the occluded LAD were determined post mortem by the tetrazolium staining technique. Nafazatrom significantly reduced the extent of irreversible myocardial ischaemic damage whether it was expressed as g/100 g left ventricle (24 +/- 4 vs. 46 +/- 6 in controls; p less than 0.01; mean +/- SEM) or as percentage of LAD risk region for infarcting (38 +/- 8 vs. 65 +/- 7% in controls; p less than 0.05). Nafazatrom did not affect peripheral haemodynamics but during drug vehicle treatment and LAD occlusion systemic blood pressure, left ventricular pressure and dP/dtmax decreased while filling pressure, heart rate, and the S-T segments of the ECG increased. The incidence of ventricular fibrillation was 8% during drug treatment and coronary ligature vs. 25% in controls (n.s.). During reperfusion, nafazatrom reduced the incidence of ventricular premature contractions and tachycardia. Ex vivo platelet aggregation in response to collagen was not inhibited by nafazatrom. Prostanoid release (thromboxane B2 and 6-keto-prostaglandin F1 alpha as breakdown products of thromboxane A2 and prostacyclin, respectively) remained unaltered in vehicle controls but nafazatrom treatment elevated prostacyclin release significantly at 4 and 5 h during LAD occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Blood Pressure; Coronary Circulation; Disease Models, Animal; Dogs; Electrocardiography; Female; Male; Myocardial Infarction; Perfusion; Platelet Aggregation; Pyrazoles; Pyrazolones; Thromboxane B2

The effects of the antithrombotic drug nafazatrom (BAY g 6575) were investigated in chloralose-anaesthetized greyhounds subject to coronary artery occlusion and reperfusion. Pretreatment with nafazatrom 10 mg/kg p.o. did not significantly reduce the number of extrasystoles or the incidence of ventricular fibrillation (VF) during the first 30 min occlusion of the left anterior descending coronary artery. However, the incidence of VF resulting from release of a 40-min coronary artery occlusion was markedly reduced (from 88% in the controls to 14% in the nafazatrom group). Both thromboxane B2 (TxB2) and 6-keto PGF1 alpha (breakdown products of TxA2 and prostacyclin respectively) were released from the acutely ischaemic myocardium in control dogs. Nafazatrom did not alter the release of TxB2 but the concentrations of 6-keto PGF1 alpha were elevated in blood draining from both the ischaemic and normal regions of the myocardium. The pronounced anti-fibrillatory effect of nafazatrom during reperfusion of the ischaemic myocardium may be related to the ability of this drug to elevate prostacyclin concentrations in the coronary circulation.

Topics: 6-Ketoprostaglandin F1 alpha; Anesthesia; Animals; Arrhythmias, Cardiac; Coronary Disease; Dogs; Epoprostenol; Female; Fibrinolytic Agents; Male; Perfusion; Prostaglandins; Pyrazoles; Pyrazolones; Thromboxane B2

We have developed an experimental model for the study of local prostaglandin production by platelets and the vessel wall following stimulation 'in vivo'. A nylon thread was inserted into the external jugular vein of rabbits; its presence did not induce an occluding thrombus. Thromboxane (TXB2) values in the blood, sampled through the facial vein, immediately distal to the stimulus, rose and remained high for at least 4 hr, while 6-keto prostaglandin (PG) F1 alpha levels, after a first increase, gradually returned to normal ('exhaustion' of the endothelial cells?). No changes were observed in the contralateral jugular vein without thread. After infusion via the femoral vein of 10 mg/kg dazoxiben, a thromboxane synthetase inhibitor, local TXB2 production was completely abolished, whereas 6-keto PGF1 alpha formation no longer returned to basal values, but tended to increase. This leads to the conclusion that upon inhibition of TXB2 formation endoperoxide metabolism is reoriented 'in vivo' towards prostacyclin, and this mainly at the site where platelets are activated. Injection of 100 mg/kg lysine acetylsalicylic acid resulted in complete inhibition of TXB2 and 6-keto PGF1 alpha formation, the latter, however, slowly recovering with time. The administration of nafazatrom to the animals did not influence the local TXB2 changes, but partially prevented the decline of 6-keto PGF1 alpha with time. The antithrombotic properties of this drug thus could be related to protection of the endothelial cells from 'exhaustion'.

Topics: Animals; Aspirin; Dinoprost; Drug Interactions; Fibrinolytic Agents; Functional Laterality; Imidazoles; Kinetics; Male; Prostaglandins F; Pyrazoles; Pyrazolones; Rabbits; Thromboxane B2; Thromboxane-A Synthase; Thromboxanes

Nafazatrom, given acutely to male volunteers, had no effect on platelet aggregation, associated thromboxane B2 (TXB2) formation or the evaluated hormonal, renal and cardiovascular parameters. Only slight increases in plasma levels of 6-keto-PGF1 alpha and in platelet counts were observed. However, a marked influence of nafazatrom on arachidonic acid metabolism in certain in vitro systems was found. Prostaglandin synthesis by rabbit kidney cortex microsomes was significantly enhanced, PGI2 being stimulated the most. In normal human platelets arachidonic acid metabolism was not influenced significantly by nafazatrom which was taken up by the platelets in a dose-dependent manner. In contrast, in platelets with a high peroxide level probably due to depletion of reducing cofactors, 12-hydroperoxy-eicosatetraenoic acid was transformed to 12-hydroxy-eicosatetetraenoic acid by nafazatrom, while the formation of TXB2 was stimulated. These findings suggest that nafazatrom may act as a reducing cofactor for the hydroperoxidase involved in the cyclooxygenase- and lipoxygenase-pathways of arachidonic acid metabolism.

Topics: 6-Ketoprostaglandin F1 alpha; Adult; Arachidonic Acids; Blood Platelets; Blood Vessels; Fibrinolytic Agents; Humans; Kidney Cortex; Male; Microsomes; Middle Aged; Platelet Aggregation; Platelet Count; Pyrazoles; Pyrazolones; Thromboxane B2