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The treatment of migraine was transformed in 1992 with the introduction of the first triptan-based therapy, subcutaneous (SC) sumatriptan. SC sumatriptan has high efficacy and a rapid onset of action compared with other available triptans and formulations presumably because of its short Tmax, high Cmax, and avoidance of enteral absorption. Because of these characteristics, SC sumatriptan is still considered the most reliably and rapidly effective self-administered medication available for acute migraine. Even so, it is relatively little used possibly in part because of patient "needle-phobia." The needle-free sumatriptan injection system (Sumavel DosePro) was developed to address this concern. Clinical trials have shown that the needle-free system is bioequivalent to needle-based injection systems, easy to use, and capable of providing rapid and effective symptom relief for many migraine episodes. Sumavel DosePro is an effective treatment for migraine and should be part of the therapeutic armamentarium, particularly in cases where a rapid onset of action is critical or where oral administration is problematic., (© 2013 American Headache Society.)

Bacterial endotoxins (lipopolysaccharide or LPS) provoke shock and tissue injury by eliciting the release of toxic factors from reticuloendothelial cells. One of the principal endogenous factors involved in this process is tumor necrosis factor alpha (TNF alpha). In this study, inhibitors selective for different classes of phosphodiesterases (PDE), were examined for their effects on LPS-induced TNF alpha production by human monocytes. The selective cAMP-PDE IV inhibitors, rolipram and RO-20-1724 were capable of inhibiting LPS-induced TNF alpha production by human monocytes in a concentration-dependent manner. Rolipram was used to examine further the cellular pharmacology of PDE IV inhibitors on cytokine production. The IC50 for inhibition of LPS-induced TNF alpha production by rolipram was 0.1 microM, whereas production of IL-1 beta or IL-6 was unaffected. Furthermore, rolipram was equally effective in inhibiting TNF alpha production by a number of other stimuli. Inhibition of TNF alpha production by rolipram was associated with an elevation of intracellular cAMP, consistent with a mechanism involving phosphodiesterase inhibition. Rolipram was efficacious in suppressing LPS-induced TNF alpha mRNA expression, and at the protein level was also active when added to cultures post-stimulated with LPS. This indicates that rolipram may act at both the transcriptional and translational levels. Rolipram inhibited TNF alpha production in vivo in a rat endotoxemia model. Collectively, these data suggest that the prototypic inhibitor of PDE IV isozyme, rolipram, can effectively and selectively inhibit LPS-induced TNF alpha production through elevation of intracellular cAMP.

The purpose of these studies was to examine the changes in renal endothelin (ET) receptor, renal function and plasma ET (ET-1) concentration in male Sprague-Dawley rats injected with nonlethal doses of Escherichia coli endotoxin (LPS). Prior to the injection of LPS, kidney ET receptor density was 59 +/- 5 fmol/mg protein (n = 20). At 24 h after the injection of 1 or 3 mg/kg LPS, [125I]ET-1 binding to kidney membranes was increased by 70% in both LPS groups (p < 0.001). Scatchard analysis of the saturation binding experiments confirmed that the increase in [125I]ET-1 binding was due to an increase in receptor density with no change in affinity (202 pmol/l at baseline and 168 pmol/l and 246 pmol/l at 24 h after the injection of 1 and 3 mg/kg LPS, respectively). At 7 days after the injection of LPS, kidney ET-1 receptor density was still increased by 30 +/- 5% and 58 +/- 16%, respectively (p < 0.05, compared to the baseline value). Baseline values for Na+ and K+ excretion were approximately 115 muEq/h and 214 +/- mu/Eq/h respectively, and were decreased with LPS. Maximal decreases in Na+ and K+ excretion occurred at 48 h (-85%) and 30 h (-82%), respectively, following the injection of 3 mg/kg LPS and returned to baseline levels in 7 days. Following the injection of 3 mg/kg LPS, plasma immunoreactive ET-1, as measured by radioimmunoassay, increased in a time-dependent manner: the maximal increase of 60% occurred within 1 h after the injection of LPS (p < 0.05), and thereafter returned to baseline levels. Kidney tissue levels of ET-1 increased from baseline values of 2.6 fmol/mg protein to a peak of 4.6 fmol/mg protein 1 h after the injection of LPS. Tissue ET-1 levels were still significantly elevated at 6 h but not 24 h after LPS injection. These studies suggest that ET-1, either by increases in plasma concentration and/or altered receptor density, may be involved in the LPS-induced impairment of renal function.

This study was designed to evaluate the cardioprotective effects of a solubilized human complement receptor, sCR1, in the rat subjected to myocardial infarction. Following coronary artery occlusion for 0.5 h and reperfusion for 24 h (MI/R group), myocardial infarct size (determined by planimetric analysis) was 18.3 +/- 2.1% of the left ventricle (n = 16), while myeloperoxidase activity (a biochemical marker of neutrophil activation) was increased from 0.94 +/- 0.09 U/g tissue in the sham occluded + vehicle group to 2.96 +/- 0.17 U/g tissue in the MI/R + vehicle treated group (P < 0.01). Injection of sCR1 (5 mg/kg i.v., 5 min prior to coronary artery occlusion) produced plasma concentrations of 154 +/- 4 microgram/ml 1 min prior to coronary artery occlusion, and concentrations of 86 +/- 2 and 58 +/- 3 micrograms/ml at 40 min and 125 min after dosing (n = 6). sCR1 reduced myocardial infarct size to 11.3 +/- 2.2% of the left ventricle, and attenuated the increase in myeloperoxidase activity to 2.11 +/- 0.20 U/g tissue (n = 18; P < 0.01, compared to the MI/R + vehicle group). Administration of sCR1 5 min prior to reperfusion afforded a 25.3% non-significant reduction in myocardial injury. These results suggest a beneficial effect of sCR1 in myocardial ischemia/reperfusion injury by reducing the infiltration of neutrophils and attenuating the extent of myocardial injury.

The present study was designed to investigate the effects of fluid administration on survival in endotoxemic or septicemic male Sprague-Dawley rats. Endotoxemia was induced by intravenous injection of Escherichia coli lipopolysaccharide (LPS), and septicemia produced by cecal ligation and puncture (CLP). In endotoxemic animals deprived of fluid resuscitation, 7-day survival following injection of LPS at doses of 1, 3, or 10 mg/kg LPS were 70% (n = 10), 30% (n = 10), and 0% (n = 10), respectively. In rats resuscitated with 3.3 ml/kg/h of 0.9% NaCl, the dose-response curve for survival was shifted 5-fold rightward in a parallel manner (p < 0.001, between the fluid-resuscitated and nonfluid resuscitated LPS groups), indicating a reduced sensitivity to the effects of LPS following fluid resuscitation. LPS increased serum tumor necrosis factor (TNF alpha) concentrations in fluid-resuscitated endotoxemic animals from a baseline value of 20 U/ml to 2,350 U/ml at 1 h, which returned to 200 U/ml at 2 h. In endotoxemic animals not receiving fluid resuscitation, serum TNF alpha levels at 1 and 2 h were 5-fold and 27-fold higher, respectively, than in fluid-resuscitated animals. There were no differences in arterial blood pressure or heart rate between the two groups of endotoxemic animals; total peripheral resistance was significantly lower at 1 h, and cardiac index was significantly greater at 3 h in the fluid-resuscitated LPS group; otherwise there were no further differences in hemodynamic parameters between the two groups. The survival rate at 4 days following CLP without fluid resuscitation was 14%, whereas CLP with fluid resuscitation improved survival to 74% (p < 0.01). TNF alpha was undetectable (i.e., < 20 U/ml) in the serum of animals subjected to CLP. The improvement in survival with fluid infusion in the LPS and CLP models cannot be attributed to catheter implantation, or to improved hemodynamic parameters in the LPS model. The improvement in survival in the LPS model with fluid infusion was associated with attenuated increases in TNF alpha levels. Furthermore, these studies illustrate that fluid-resuscitated and nonfluid-resuscitated experimental animal models should not be considered equivalent.

The purpose of this study was to evaluate the effects of carvedilol, a beta 1&2-adrenergic blocker and vasodilator, on cirazoline-mediated changes in arterial blood pressure and isoproterenol-mediated changes in heart rate after acute and chronic administration. Conscious, chronically instrumented male Sprague-Dawley rats were injected with carvedilol (1 mg/kg, IV), prazosin (0.3 mg/kg, IV), or propranolol (1 mg/kg, twice daily for 8 days. After administration of the first dose of carvedilol on day 1, the vasopressor response to cirazoline (60 +/- 3 mmHg predrug) and the isoproterenol-induced tachycardia (152 +/- 13 beats/min predrug) were blocked (e.g., 7 +/- 4 mmHg postdrug and 11 +/- 3 beats/min postdrug, respectively). After the administration of carvedilol on day 8, the cirazoline vasopressor response was 2 +/- 1 mmHg and the isoproterenol-induced tachycardia was 4 +/- 3 beats/min, indicating effective alpha 1- and beta-adrenergic blockade after chronic dosing with carvedilol. Prazosin blocked the cirazoline-induced vasopressor response on both days 1 and 8 but had no effect on the isoproterenol-induced tachycardia. Propranolol blocked the isoproterenol-induced tachycardia on both days 1 and 8 but had no effect on the cirazoline vasopressor response. These data indicate that only carvedilol effectively blocked both alpha- and beta-adrenergic hemodynamic responses and that the antagonism of these responses with carvedilol was not diminished after chronic dosing of twice-a-day treatment for 8 days.

This study was designed to investigate the changes in tissue content and plasma concentrations of CGRP, a 37 amino acid vasoactive peptide, in male Sprague Dawley rats injected intravenously with a nonlethal dose of 3 mg/kg E. coli endotoxin. Plasma CGRP concentrations in nonendotoxemic animals, measured by a specific RIA, were initially 30.5 +/- 3.3 pg/ml, and were significantly increased to 63.7 +/- 4.6 pg/ml 2 hr after induction of endotoxemia (P less than 0.001; n = 13). A higher dose of LPS did not further elevate plasma CGRP levels, indicating that the maximal response occurred following a dose of 3 mg/kg LPS. CGRP levels in abdominal aorta, inferior vena cava, stomach, kidney, and left ventricular myocardium (4.11, 8.5, 2.61, 0.69, and 0.25 pmol/g wet weight tissue, respectively) were not changed significantly following the injection of endotoxin. However, in lung and mesenteric artery the levels increased significantly from 1.47 +/- 0.12 and 7.97 +/- 1.32 pmol/g wet weight tissue to 1.96 +/- 0.19 (P less than 0.05, n = 11) and 15.02 +/- 2.3 pmol/g (P less than 0.01; n = 7), respectively. In contrast, CGRP levels in the duodenum were significantly decreased from 11.3 +/- 0.93 pmol/g wet weight tissue to 6.2 +/- 0.68 pmol/g (P less than 0.001; n = 6). The changes in plasma concentration and tissue content of CGRP suggest that splanchnic organs may be the source of the elevated plasma CGRP levels in endotoxemia and that selective organ CGRP levels reflect a role in the pathogenesis of the response to endotoxemia.

The present study evaluates the biological responses to 10% blood volume infusion ("top-loading," n = 7) or 50% blood volume exchange transfusion (n = 8) with a new preparation of liposome-encapsulated hemoglobin (LEH) in the conscious rat. Top-loading did not affect systemic hemodynamic variables but induced transient thrombocytopenia (-36% +/- 7%; P less than 0.05) and elevation of plasma thromboxane B2 (12.4 +/- 3.8 pg/100 microliters vs. undetectable levels at the control; P less than 0.05). Rats exchanged with LEH maintained mean arterial pressure (MAP) during the 3 hr observation period, whereas control (0.9% NaCl or lactated Ringer's solution) animals developed hypotension (-23 +/- 5 mm Hg, P less than 0.05). The maintenance of MAP in the LEH group resulted from the opposing effects of LEH-induced increase in total peripheral resistance index (TPRI; +0.06 +/- 0.01 mm Hg/ml/min/kg; P less than 0.05), and decreased cardiac index, (Cl, -25 +/- 6 ml/min/kg, P less than 0.05). In contrast, the decline in MAP in the control groups could be attributed to the lower Cl (-65 +/- 8 ml/min/kg; P less than 0.05). All rats developed metabolic acidosis (base excess of -9.7 +/- 0.6 mmol/liter; P less than 0.05), which was transient in the LEH group but progressive in the control groups. These data support the possible use of LEH as a blood substitute when massive transfusions are needed.

G619, a 4-OH-isophthalic acid derivative, was studied for its capacity to inhibit platelet aggregation. G619 dose-dependently inhibited U46619, collagen, ADP, PAF, thrombin and epinephrine-induced platelet aggregation in vitro. The IC50 values for inhibition of U46619-induced human and rabbit platelet aggregation were 39 and 43 microM, respectively. G619, at 100 microM, inhibited high concentration collagen (10 micrograms/ml)-induced aggregation of rabbit platelets pretreated with indomethacin and increased the level of cAMP in washed rabbit platelets by 30% (p less than 0.01 vs basal). However, G619, did not inhibit fibrinogen binding to GPIIb/IIIa receptor, phosphodiesterase, U46619-induced contractile responses on canine saphenous vein or rabbit aorta, calcium-induced vasoconstriction and thrombin or PAF-induced elevation of [Ca++]i in platelets in vitro. In vivo, the U46619-induced maximal thrombocytopenia in rats was reduced from 40% (vehicle) to 22% and 18% by 10 and 30 mg/kg of G619 i.v., respectively. G619 (30 mg/kg) had no effect on the U46619-induced vasopressor response or sudden death in rats, and had no effect on TxB2 formation. Our results indicate that G619 is a broad-spectrum platelet aggregation inhibitor and may have its effect on a common mechanism for platelet aggregation besides an effect on the thromboxane A2 receptor.

Objective: The aim was to evaluate in a minipig model of acute myocardial infarction the cardioprotection provided by the beta adrenoceptor blocking and vasodilating activities present in carvedilol; comparison was made to the pure beta adrenoceptor antagonist, propranolol., Methods: Experiments were performed in 25 Yucatan minipigs (9-12 kg), randomly assigned to receive vehicle (n = 7), carvedilol 0.3 mg.kg-1 (n = 6), carvedilol 1 mg.kg-1 (n = 6), or propranolol 1 mg.kg-1 (n = 6). Myocardial infarction was produced by occlusion of the left anterior descending coronary artery for 45 min followed by 4 h of reperfusion. Vehicle, carvedilol (0.3 and 1 mg.kg-1) or propranolol (1 mg.kg-1) were given intravenously 15 min before the coronary artery occlusion. At the end of the reperfusion period, infarct size was determined using Evans blue dye and triphenyltetrazolium chloride staining. Infarct volumes were visualised using computer assisted three dimensional image analysis of the stained myocardial tissue sections. Myeloperoxidase activity was measured in tissue samples removed from normal, infarcted, and at risk areas., Results: Carvedilol (1 mg.kg-1) reduced infarct size by over 90% without producing pronounced changes in systemic haemodynamic variables. The ability of carvedilol to reduce infarct size was clearly dose dependent. Thus infarct size, which represented 27.5(SEM 2.3)% of the area at risk in the vehicle treated group, was only 13.1(4.0)% (p < 0.05) and 2.4(1.5)% (p < 0.01) in pigs treated with carvedilol at 0.3 and 1 mg.kg-1, respectively. In animals treated with propranolol (1 mg.kg-1), infarct size represented 10.9(2.4)% of the area at risk (p < 0.05). The 60% and 91% reductions in infarct size produced by propranolol (1 mg.kg-1) and carvedilol (1 mg.kg-1), respectively, were clearly evident upon three dimensional image analysis. The reduction in infarct size was significantly greater for carvedilol (1 mg.kg-1) compared to propranolol (1 mg.kg-1) at equivalent beta adrenoceptor blocking doses. Pretreatment with propranolol did not reduce the increases in myeloperoxidase activity observed in the area at risk or in the infarcted area. In contrast, carvedilol produced a dose dependent reduction in myeloperoxidase activity in these areas., Conclusions: Carvedilol limits myocardial necrosis resulting from coronary artery occlusion and reperfusion in a more pronounced manner than the pure beta adrenoceptor antagonist, propranolol. The cardioprotective effect of carvedilol, which reduced infarct size by 91%, may result from the combined effects of beta adrenoceptor blockade and vasodilatation, and possibly also from inhibition of intracellular calcium overload in cardiac cells resulting from antagonism of myocardial alpha 1 adrenoceptors and/or calcium channel blockade. The cardioprotection provided by carvedilol may ultimately be of benefit in hypertensive patients who are at risk for acute myocardial infarction.

The purpose of this study was to evaluate the cardioprotective effects of carvedilol, a beta-adrenergic blocker and vasodilator, in two models of ischemic myocardial damage in the rat. Following coronary artery occlusion for 0.5 h and reperfusion for 24 h (MI/R group), left ventricular (LV) injury was determined by planimetric analysis of triphenyltetrazolium chloride-stained tissue, and polymorphonuclear leukocyte infiltration was assessed by measuring myeloperoxidase (MPO) activity. In the vehicle-treated MI/R group, infarct size was 14.2 +/- 1.3% of the LV (n = 16), and MPO activity was increased to 2.8 +/- 0.7 from 0.14 +/- 0.03 U/g tissue in the vehicle-treated sham-occluded group (p less than 0.01). Carvedilol (1 mg/kg i.v., 15 min prior to coronary artery occlusion and at 3.5 h following reperfusion) reduced myocardial infarct size to 7.5 +/- 1.2% of the LV (n = 14; p less than 0.01) and attenuated the increase in MPO activity to 1.4 +/- 0.4 U/g tissue (p less than 0.05). A lower dose of carvedilol (i.e. 0.3 mg/kg i.v.) did not limit myocardial infarct size or the increase in MPO activity. In a model of permanent coronary artery occlusion, 24-hour survival was reduced from 85% in sham-occluded animals (n = 38) to 44% in the vehicle-treated MI group (n = 84; p less than 0.01). In comparison to the vehicle-treated MI group, carvedilol (0.3 mg/kg i.v., 15 min prior to coronary artery occlusion and 1 mg/kg 4 h after occlusion) improved survival by 55% (n = 64; p less than 0.05, compared to the vehicle-treated MI group), whereas the same dose of propranolol (n = 42) had no significant effect on survival. These results indicate that carvedilol reduces myocardial ischemia/reperfusion injury, and significantly improves survival in a permanent coronary artery occlusion model of myocardial infarction.

Carvedilol is a multiple-action cardiovascular agent that is both a beta-adrenoceptor antagonist and a vasodilator and has recently been made available for the treatment of mild-to-moderate hypertension. Clinical trials are ongoing to establish the efficacy of carvedilol in angina and congestive heart failure. beta-Adrenoceptor antagonists are known to reduce myocardial work secondary to reductions in heart rate and contractility; accordingly, they have been shown to be cardioprotective in animals and in humans. Because carvedilol has beta-adrenoceptor antagonist activity, it also should provide significant cardioprotection. The additional vasodilating activity of carvedilol, which will further reduce myocardial work by decreasing afterload and myocardial wall tension, should provide more salvage of ischemic myocardium than that afforded by a pure beta-adrenoceptor antagonist, such as propranolol. We investigated the ability of carvedilol and propranolol to reduce infarct size in experimental models of acute myocardial infarction in the rat, pig, and dog. The left anterior descending coronary artery was occluded for 30 (rat) or 45 min (pig) and then reperfused for 24 h (rat) or 4 h (pig). In the dog, the left circumflex coronary artery was occluded for 60 min and reperfused for 24 h. Vehicle, carvedilol, or propranolol was administered intravenously 15 min before ischemia (and, in the rat only, repeated 4 h after ischemia). An additional group of dogs was subjected to permanent left anterior descending coronary artery occlusion for 6 h, and carvedilol or propranolol was given 15 min after occlusion. Infarct size was examined on stained tissue sections using quantitative image analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

We evaluated the effects of SK&F 86002, a dual 5-lipoxygenase/cyclooxygenase inhibitor, on the responses to 30 mg/kg Escherichia coli endotoxin (bacterial lipopolysaccharides, LPS) in conscious male Sprague-Dawley rats. Injection of LPS increased serum tumor necrosis factor (TNF alpha) activity from 20 U/ml (baseline) to 1,066 +/- 430 and 2,825 +/- 1,155 U/ml (n = 9) at 30 min and 1 h after administration of LPS, respectively (p less than 0.01 as compared with the vehicle control group). This dose of LPS reduced the survival rate to 9% at 48 h (mean survival time 9.7 +/- 2.7 h), increased heart rate (HR) to 494 +/- 18 beats/min, increased the hematocrit to 56 +/- 2 vol%, reduced the circulating platelet count at 6 h to 40% of the initial value, and produced leukopenia of 30% of the initial value at 1 h, with recovery to the initial value at 6 h. Administration of 30 mg/kg SK&F 86002 (intragastric, i.g.) 1 h before injection of LPS reduced serum TNF alpha concentrations to 92 +/- 58 and 184 +/- 117 U/ml at 30 min and 1 h (p less than 0.05), respectively, and also reduced the hemoconcentration. The survival rate was improved to 60% (mean survival time 38.1 +/- 4.3 h; p less than 0.05), although there was no effect on the hemodynamic responses to LPS. SK&F 86002 significantly reduced thrombocytopenia at 30 min and 1 h (p less than 0.05), but not at 3 and 6 h, and had no effect on changes in white blood cell (WBC) count.(ABSTRACT TRUNCATED AT 250 WORDS)

The benefit of thrombolytic agents to reduce myocardial infarct size, improve left ventricular (LV) function, and prolong survival in human subjects is generally recognized, although the precise mechanism is poorly defined. This study was designed to evaluate the cardioprotective effects of streptokinase (SK) in rats, a species less responsive to plasminogen activators, using a model of mechanical occlusion and release of the left coronary artery. Myocardial injury and polymorphonuclear leukocyte (PMN) infiltration were determined by measuring creatine phosphokinase (CPK) specific activity and myeloperoxidase (MPO) activity, respectively, in the LV free wall (LVFW). After coronary artery occlusion for 0.5 h and reperfusion for 24 h (myocardial ischemia, MI/R), CPK specific activity decreased from 7.0 +/- 0.3 U/mg protein in the sham + vehicle group to 5.6 +/- 0.5 U/mg protein in the MI/R + vehicle group (n = 19, p less than 0.01), while MPO activity increased from 0.14 +/- 0.03 U/g tissue in the sham + vehicle group to 2.8 +/- 0.7 U/g in the MI/R + vehicle group (p less than 0.001). Administration of SK (100,000 IU/kg + 50,000 IU/kg/h for 2 h beginning 15 min before coronary artery reperfusion) reduced the loss of CPK specific activity from reperfused myocardium (6.8 +/- 0.5 U/mg protein, n = 23, p less than 0.05 as compared with the MI/R + vehicle group) and attenuated the increase in MPO activity (1.3 +/- 0.4 U/g tissue, p less than 0.05 as compared with the MI/R + vehicle group). This dose of SK did not change plasma fibrinogen concentration, slightly reduced plasminogen activity (i.e., 20% from control value), and markedly reduced alpha 2-antiplasmin activity (i.e., 60% from control values). A lower dose of SK (i.e., 10,000 IU/kg + 5,000 IU/kg/h for 2 h) did not reduce myocardial injury, did not attenuate the increase in MPO activity, and had no effect on the measured hemostatic parameters. Survival in all MI/R groups ranged from 62 to 66%, and there were no differences in survival between any of the groups (p greater than 0.05). In a model of arachidonic acid-induced rat hindpaw inflammation, SK had no effect on the increase in MPO activity, suggesting that the increase in myocardial MPO activity was not due to a direct effect on inflammatory cell accumulation. In in vitro studies, SK (1-1,000 U/ml) did not scavenge superoxide anion produced by purine (10 mM) and xanthine oxidase (10 mU/ml), nor did it reduce superoxide release, beta-glucuronidase release, or neutrophil aggregation of rabbit peritoneal neutrophils activated with fMLP.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of a selective LTD4 receptor antagonist SK & F104353 was studied in septic pigs anesthetized with isoflurane. Yorkshire pigs (25.2 +/- 2.3 kg) were instrumented and monitored for cardiac output (CO), mean arterial pressure (MAP), systemic vascular resistance (SVR), mean pulmonary arterial pressure (MPAP), pulmonary vascular resistance (PVR), renal artery blood flow (RABF), renal vascular resistance (RVR), arterial PO2, and extravascular lung water (EVLW). Blood samples were also collected for platelet, white blood cell and hematocrit determinations and plasma was assayed for thromboxane (TX) B2. Sepsis was induced by infusion of Pseudomonas aeruginosa (3 x 10(8) CFU%kg/h) for 2 h. Cardiovascular and hematologic data were determined at 30 min intervals for 4 h. Groups were infused with either SK & F104353 (3 mg/kg/h; n = 5) or drug vehicle (n = 6) beginning 15 min prior to infusion with the P. aeruginosa. In the vehicle group beginning at -90 min after sepsis induction, there was a 30 +/- 7% decrease of CO, a 27 +/- 5.0% decrease of MAP, and a 44 +/- 7% decrease of RABF, whereas, MPAP increased to 147 +/- 37% and plasma TXB2 increased from less than 200 pg/ml to 3,049 +/- 367 pg/ml (P less than 0.05). The EVLW and hematocrit increased (P less than 0.05), and the arterial PO2, white blood cell count, and platelet count decreased with the severity of the sepsis. In pigs pretreated with SK & F104353 the MAP and RABF were transiently improved (P less than 0.05), and the decrease in arterial PO2 was delayed.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelin-1 (ET-1) is a recently described potent vasoconstrictor peptide. Plasma and myocardial tissue levels of ET-1 are increased following myocardial ischemia, however, the factors which regulate ET-1 binding sites in vivo are not well understood. ET-1 binding sites were measured by Scatchard analysis of [125I]ET-1 binding to membranes of rat myocardium. The highest number of ET-1 binding sites (2,951 fmol/mg protein) were found in right atrial tissue, and followed the rank order of right atrium greater than left atrium (2,157 fmol/mg protein), greater than right ventricle (835 fmol/mg protein), greater than septum (609 fmol/mg protein) = left ventricle (498 fmol/mg protein). Following coronary artery occlusion for 24 h, ET-1 binding sites of left atrium were decreased by 35% (p less than 0.01), without a change in the Kd (i.e., 98 pM). Other regions of the myocardium did not exhibit any change in the number of ET-1 binding sites. Similarly, no change in ET-1 binding sites were observed following coronary artery occlusion for 0.5 h followed by 24 h reperfusion. These data indicate that there exists considerable regional differences in the density of ET-1 binding sites in the myocardium, and that ET-1 sites are selectively reduced in left atrial tissue following myocardial infarction.

BN 50739, a new PAF receptor antagonist, was tested in vitro and in vivo for its capacity to block PAF, endotoxin and recombinant human tumor necrosis factor-alpha (rTNF)-mediated effects. In vitro, BN 50739 blocked PAF-induced platelet aggregation by 60 to 100% at 0.2-1 x 10(-7) M (P less than .002), respectively. In the conscious rat, pretreatment (30 min) with BN 50739 (n = 5-13) dose-dependently attenuated PAF-induced hypotension (-5 +/- 5 vs. - 43 +/- 2 mm Hg, P less than .01) and shortened the recovery time of mean arterial pressure (22 +/- 13 vs. 325 +/- 46 sec, P less than .01). BN 50739 (10 mg/kg i.p., n = 5-11) prevented endotoxin (14.4 mg/kg) induced-hemoconcentration (54 +/- 1 vs. 46 +/- 1%, P less than .01) and reduced 24-hr mortality (100 vs. 60%, P less than .05). Only partial protection was conveyed by BN 50739 against the hypotensive response to endotoxin (115 +/- 3 vs. 91 +/- 4 mm Hg, P less than .03). Also, BN 50739 attenuated the lipopolysaccharide-induced elevation of plasma thromboxane B2 (21.2 +/- 0.8 vs. 46.7 +/- 11.8 pg/100 microliters, P less than .01) and tumor necrosis factor-alpha (7523 +/- 3983 vs. 26,430 +/- 3541 U/ml, P less than .05), whereas leukopenia and thrombocytopenia remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

1. The purpose of these experiments was to investigate the effects of the selective peptidoleukotriene receptor antagonist, SK&F S-106203, on leukotriene C4 (LTC4), LTD4 and LTE4 vasopressor responses in the conscious, normotensive rat. SK&F S-106203 was administered as a bolus followed by a continuous infusion in order to provide information on the relationship between antagonism of leukotriene responses and steady-state plasma concentrations. 2. Infusion of SK&F S-106203 at doses of 0.2 mgkg-1 + 1 mgkg-1 h-1, 1 mgkg-1 + 3 mgkg- h-1 or 2 mgkg-1 + 10 mgkg-1 h-1 produced dose-dependent steady-state plasma drug concentrations of 1.0, 3.2 and 23.8 micrograms ml-1, respectively. Plasma SK&F S-106203 concentrations appeared to increase in a linear fashion at doses of 1 and 3 mgkg-1 h-1; at the highest dose the increment in plasma drug concentrations (i.e., 7-8 fold) was greater than the increment in dose (i.e., 3 fold), suggesting saturation of the primary clearance mechanism(s) at this dose. 3. SK&F S-106203 (2 mgkg-1 + 10 mgkg-1 h-1) had no effect on noradrenaline-, vasopressin-, isoprenaline-, or U 46619-induced responses. 4. SK&F S-106203 produced dose-dependent rightward shifts in the LTC4 and LTE4 dose-response curves. Administration of SK&F S-106203 at doses of 0.2mg kg1 + 1 mg kg1 h-, mg kg' + 3mgkg-'h-1, or 2mgkg-' + lOmgkg-1h'- produced dose-ratios of 1.0, 3.1 and 19.9, respectively, against LTC4 responses, and dose-ratios of 1.6, 3.8 and 9.1, respectively, against LTE4 responses. 5. Against LTD4 responses, SK&F S-106203 at doses of 0.2mgkg- + mgkg-1 h-, mg kg' + 3 mg kg- 1h - ', or 2 mg kg- + 10 mg kg- h- produced dose-ratios of 2.5, 2.8, and 11.4, respectively. Administration of D-penicillamine, a non-competitive LTD4 dipeptidase inhibitor, had no effect on LTD4 responses. 6. The similarity in the LTD4 dose-ratios at the two lower infusion rates, despite increases in the plasma drug concentrations, suggests the existence of pharmacologically heterogeneous LTD4 receptors. These results indicate that SK&F S-106203 is a potent, selective and apparently competitive antagonist of LTC4, LTD4 and LTE4 vascular responses in the intact rat.

The purpose of these studies was to evaluate the effects of the peptidoleukotriene (LT) receptor antagonist, ICI 198615, on the vasopressor responses produced by LTC4, LTD4 and LTE4. Conscious, normotensive rats were prepared with arterial and venous catheters for measurement of changes in arterial blood pressure and administration of drugs, respectively. Complete dose-response curves were first generated to LTC4, LTD4 and LTE4: those agents produced dose-dependent increases in arterial blood pressure, with ED20 values (i.e. dose to increase blood pressure 20 mm Hg) of 1.7 +/- 0.2, 2.1 +/- 0.2 and 19.8 +/- 3.7 nmol/kg i.v., respectively. ICI 198615 (intravenous bolus followed by a continuous infusion) produced dose-dependent, parallel shifts to the right in the LTC4 dose-response curve. At doses of 0.2 mg/kg + 1 mg/kg/h, 1 mg/kg + 3 mg/kg/h or 2 mg/kg + 10 mg/kg/h, ICI 198615 produced dose ratios of 4.5, 17.1 and 50.0, respectively. Against LTD4 responses, ICI 198615 at a dose of 0.1 mg/kg + 0.3 mg/kg/h produced a dose ratio of 3.4, whereas at doses of 0.2 mg/kg + 1 mg/kg/h, 1 mg/kg + 3 mg/kg/h or 2 mg/kg + 10 mg/kg/h ICI 198615 produced dose ratios of 16.3, 24.9 and 16.2, respectively. The difference in the dose ratios between these three groups was not statistically significant (p greater than 0.05). However, a dose of 10 mg/kg + 30 mg/kg/h produced a dose ratio of greater than 100. Against LTE4 responses, ICI 198615 at doses of 0.2 mg/kg + 1 mg/kg/h or 1 mg/kg + 3 mg/kg/h produced dose ratios of 4.1 and 11.3, respectively. The similarity in the LTD4 dose ratios despite a 3- or 10-fold increase in the dose of ICI 198615 suggests the existence of high- and low-affinity LTD4 receptor sites, whereas the responses to LTC4 and LTE4 appeared to be mediated via a single receptor population. These results indicate that ICI 198615 is a potent and competitive antagonist of LTC4, LTD4 and LTE4 vascular responses in the rat.

Vascular bed reactivity to exogenous LTD4 and blockade of these responses by a selective LTD4 receptor antagonist, SK&F 104353, were studied. Yorkshire pigs (N = 13; 25.8 +/- 1.4 kg) were anesthetized with isoflurane, and monitored for cardiac output (CO), mean pulmonary artery pressure (MPAP), pulmonary capillary wedge pressure (PCWP), right ventricular stroke work (RVSW), mean arterial pressure (MAP), renal artery blood flow (RABF), pulmonary vasculature resistance (PVR), renal vascular resistance (RVR), and systemic vascular resistance (SVR). LTD4 (0.03, 0.1, 0.3, 1, 3 and 10.0 micrograms/kg) was given intravenously. The MPAP, MAP, and RABF were recorded at baseline and for 20 min after the injection of LTD4. SK&F 104353 was infused (3 mg/kg/h, i.v.) and the dose-response to LTD4 was repeated. LTD4 induced changes in the MPAP, PCWP, MAP, and RABF. SK&F 104353 attenuated LTD4 induced changes in the MPAP, PVR, RABF and RVSW. MPAP was increased 123 +/- 24% and 115 +/- 10%, respectively, in pigs given 3.0 and 10 micrograms/kg doses, and increased to only 36 +/- 9% at a 10 micrograms/kg dose of LTD4 in animals pretreated with SK&F 104353 (P less than 0.05). MPAP was not increased at the 3.0 micrograms/kg dose, and increased to only 36 +/- 9% at a 10 micrograms/kg dose of LTD4 in animals pretreated with SK&F 104353 (P less than 0.05). These changes were paralleled by a reduction in PVR. RABF was decreased 76 +/- 5% and 83 +/- 7%, respectively, at the 3.0 and 10 micrograms/kg dose of LTD4.(ABSTRACT TRUNCATED AT 250 WORDS)

The ability of six non-steroidal anti-inflammatory agents--meclofenamate, indomethacin, flurbiprofen, naproxen, ibuprofen, and acetylsalicylic acid--to inhibit coronary constriction induced by the thromboxane agonist carbocyclic thromboxane A2 (CTA2) was studied in isolated perfused cat coronary arteries. At constant flow, 7.5 nM CTA2 increased coronary artery perfusion pressure by 33 +/- 3 mm Hg (n = 20). Sodium meclofenamate reduced 7.5 nM CTA2-induced vasoconstriction by 2% at 0.34 microM (ns), 38% at 3.4 microM (ns), and 99% at 34 microM (p less than 0.025). The IC50 for meclofenamate was 5.4 microM; the IC50 for indomethacin, flurbiprofen, naproxen, ibuprofen, and acetylsalicylic acid was 42, 150, 250, 485, and 610 microM, respectively. Increasing the external calcium concentration to 10 mM completely reversed the inhibition of CTA2-induced coronary vasoconstriction. Furthermore, the data suggest that inhibition of CTA2-induced coronary vasoconstriction by anti-inflammatory agents may be explained either by thromboxane receptor antagonism or calcium channel blockade.

This study was designed to assess the effect of a peptidoleukotriene receptor antagonist, SK&F 104353, for limiting myocardial damage and neutrophil accumulation in rats subjected to myocardial reperfusion injury (MI/R). In conscious rats, SK&F 10,4353 (25 mg/kg, i.v.) antagonized LTD4-induced vasopressor responses by 90% and 60% at 1 and 4 hr, respectively, indicating effective blockade of peptido-leukotriene responses. In another group of animals subjected to 30 min of coronary artery occlusion with reperfusion for 24 hr, myocardial injury and neutrophil infiltration were determined by measuring creatine phosphokinase (CPK) specific activity and myeloperoxidase (MPO) activity, respectively, in the left ventricular free wall (LVFW). Myocardial CPK levels were 8.1 +/- 0.2 U/mg protein in Sham-MI/R vehicle-treated animals, and were significantly decreased to 6.4 +/- 0.6 U/mg protein in MI/R-vehicle animals. Myocardial MPO values were 1.5 +/- 0.5 U/g LVFW in Sham-MI/R vehicle-treated animals, and significantly increased to 4.3 +/- 0.6 U/g LVFW in MI/R-vehicle animals. Administration of SK&F 10,4353 (25 mg/kg, i.v.) 1 min prior to coronary occlusion and 3.5 hr post reperfusion had no effect on the loss of myocardial CPK specific activity or the increase in MPO levels (p greater than 0.05, compared to the MI/R-vehicle group). Thus, at a dose that antagonized LTD4-induced vasopressor responses, SK&F 104353 did not attenuate either the extent of myocardial injury or inflammatory cell accumulation associated with myocardial ischemia/reperfusion. These results suggest that peptidoleukotrienes do not contribute to the progression of myocardial ischemic/reperfusion injury.

The purpose of this study was to compare the effects of dazoxiben (DAZ), UK 38,485 (UK) and aspirin (ASA) in the prevention of thrombotic sudden death in rabbits. In anesthetized male rabbits, sudden death was produced by intravenous administration of 0.75 mg/kg arachidonic acid (AA). AA increased plasma TxB2 levels from 0.20 +/- 0.10 ng/ml to 8.75 +/- 1.79 ng/ml and produced a 42% reduction in the number of circulating platelets. Death occurred in all animals within 5 minutes. Administration of DAZ (8.6 mumole/kg) 15 min before AA prevented the increase in plasma TxB2, the thrombocytopenia and sudden death while pretreatment with DAZ 2 hr before AA did not. The administration of UK (8.6 mumole/kg) 15 min. 4 hrs or 8 hrs before AA resulted in 100%, 67% and 33% survival, respectively. ASA (110 mumole/kg) administered 2 or 24 hrs before AA inhibited the increase in plasma TxB2 and prevented the fall in platelet counts. All animals pretreated with ASA survived. These data demonstrate that DAZ and UK have only a short to moderate duration of action in preventing AA-induced increases in plasma Tx levels and thrombocytopenia.

In vitro experiments indicate that thromboxane A2 (TA2) is a potent platelet aggregator and vascular constrictor. However, it is unclear what roles these specific actions may contribute in the pathophysiology of myocardial ischemia. Carbocyclic thromboxane A2 (CTA2), a TA2 analog, constrict isolated perfused cat coronary arteries, but does not aggregate platelets, and thus appeared useful to clarify these separate actions of TA2. In anesthetized cats, radioactive labeled microspheres were injected into the left atrium for measurement of cardiac output and tissue blood flows. Compared to control measurements, CTA2 infusion (4.8 microgram.kg-1.min-1 for 10 min) significantly decreased cardiac output from 347 to 16 ml.min-1 to 248 +/- 16 ml.min-1 (p less than 0.025). Furthermore, CTA2 also significantly reduced blood flow to the left ventricle by 33 +/- 7%, but did not alter heart rate or MABP in the intact cat. In cats subjected to left anterior descending coronary artery occlusion, infusion of CTA2 (1 microgram.min-1 for 120 minutes) 30 min after ligation resulted in a significantly reduced myocardial cellular integrity as measured by myocardial creatine kinase activity (p less than 0.01) or percent bound myocardial cathepsin D (p less than 0.01). Thus, these data suggest that activation of vascular thromboxane receptors as well as direct cellular damage may play a role in the pathophysiology of myocardial ischemia.

Endotoxin shock was induced in anesthetized cats with E. coli endotoxin (5 mg/kg, i.v.) This produced a severe decline in mean arterial blood pressure and a marked decrease in superior mesenteric artery flow (SMAF) within 1 h. The plasma activity of cathepsin D, a lysosomal protease, increased 6-fold by 2 h. At 5 h, myocardial depressant factor (MDF), a toxic of 0.75 nmol.kg-1.min-1 dilated the splanchnic circulation and significantly increased SMAF. In addition, PGI2 almost completely prevented the accumulation of cathepsin D and MDF in the circulating blood of cats given endotoxin. These findings suggest that PGI2 exerts a variety of beneficial actions in endotoxin shock including vasodilation and stabilization of lysosomal membranes. In addition, PGI2 is known to prevent platelet aggregation and suppress thromboxane formation, two additional effects that may be of positive survival value in endotoxin shock.

The purpose of this study was to examine the effects of the peptidoleukotriene receptor antagonist, SK&F 104353, on the responses to endotoxin in conscious male Sprague-Dawley rats. Administration of Salmonella enteritidis endotoxin (30 mg/kg i.v.; LD90) resulted in a decrease in the number of circulating platelets, leukopenia, an increase in hematocrit, and 0% survival at 24 hr. Pretreatment with SK&F 104353 (1 mg/kg, i.v. bolus followed by 3 mg/kg/hr, i.v. infusion for 6 hr) 5 min before injection of endotoxin produced steady state plasma drug levels of 1.6 micrograms/ml in naive animals and levels of approximately 3.4 micrograms/ml in endotoxemic animals (P less than 0.05). SK&F 104353 significantly attenuated the endotoxin-induced thrombocytopenia (P less than 0.05) but had no effect on either the endotoxin-induced early leukopenia or late leukocytosis. Additionally, SK&F 104353 significantly reduced the endotoxin-induced hemoconcentration (P less than 0.05) and improved survival to 30% at 48 hr (P less than 0.05). A higher dose of SK&F 104353 (2 mg/kg, i.v. bolus followed by 10 mg/kg/hr, i.v. infusion for 6 hr) did not produce any further benefit. These data indicate clearly the pathophysiologic role of peptidoleukotrienes in endotoxemia and suggest SK&F 104353 could be useful for ameliorating some of the deleterious sequelae associated with this condition.

Pinane thromboxane A2 (PTA2), a thromboxane A2 analog has been shown to antagonize the vasoconstriction and platelet aggregation induced by thromboxane A2, in addition to specifically inhibiting thromboxane synthetase. Because thromboxane A2 generation would be detrimental in acute myocardial ischemia (MI) by both decreasing coronary blood flow and increasing platelet aggregation, inhibition of thromboxane production and action may be beneficial in myocardial ischemia. In pentobarbital-anesthetized cats, the left anterior descending coronary artery was ligated, and PTA2 (0.5 mumol . kg-1 . h-1) or a Na2CO3 vehicle was infused 30 min post-MI for 270 min. Compared to vehicle-treated MI cats, PTA2 prevented the increase in plasma thromboxane levels seen at 2 through 5 h (P less than 0.005 at 2 through 5 h) and prevented the large increase in plasma CK activities at 4 and 5 h (P less than 0.025). In addition, PTA2 treatment abolished the differences in myocardial CK activities between ischemic and nonischemic regions and prevented the decrease in percent-bound cathepsin D in the ischemic region. Moreover, ECG analysis revealed a decreased incidence of premature beats in PTA2-treated MI cats as compared to MI-vehicle cats. In summary, these data indicate that PTA2 protects the ischemic myocardium and provide further evidence that inhibition of thromboxane formation, in addition to antagonism of its activity, is beneficial during the early stages of acute myocardial ischemia.

The vasoactive metabolites of arachidonic acid TxA2 and sulfidopeptide-leukotrienes appear to play a role in mediating hemodynamic alterations in endotoxic shock. The ultimate goal of these and other studies in shock is, however, to understand the mechanisms underlying the pathogenic changes in human shock states in order to develop effective treatment. Recent studies (see reviews by Ball, 1988) have implicated eicosanoids in pathogenesis of shock in man confirming the directions provided by the bolus endotoxin studies and suggest additional investigations of hemodynamics following interventions designed to alter eicosanoid synthesis in shock.

This study was designed to assess the effectiveness of the thromboxane receptor antagonist, BM 13.505, in limiting myocardial infarct size in rats subjected to 30 min of coronary artery occlusion followed by reperfusion for 5.5 hr (MI/R). Myocardial infarct size was determined histochemically with triphenyltetrazolium chloride staining of the left ventricle. BM 13.505 (30 mg/kg, i.p.) was administered 1 min prior to coronary artery occlusion. In MI/R-vehicle treated animals, myocardial infarct size was 39 +/- 6% of the left ventricle. In MI/R-BM 13.505 treated animals, reperfusion injury was reduced by 50% to 19 +/- 7% of the left ventricle (p less than 0.05, compared to the MI/R-vehicle group). There were no significant differences in mean arterial blood pressure, heart rate, platelet count or white blood cell count between the treatment groups. Incubation of cultured L929 cells with the thromboxane/endoperoxide mimetic U 46619 produced a cytolytic effect, with an EC50 value of 125 microM. Addition of BM 13.505 at concentrations up to 30 microM did not protect against the cytolytic effect of U 46619, suggesting a non-receptor-mediated mechanism. These data indicate that hemodynamic, hematologic or cytoprotective factors do not explain the cardioprotective effects of BM 13.505. These results provide further evidence that antagonism of thromboxane receptors is beneficial in myocardial ischemia/reperfusion injury.

A number of reports indicate the TX receptor antagonists may be useful in preventing coronary artery reocclusion following fibrinolytic therapy, reducing myocardial ischemia/reperfusion injury and consequent neutrophil accumulation, preventing thrombocardiac sudden death, and attenuating the sequelae of endotoxic shock. Limited clinical studies have been initiated, and no adverse clinical effects can be associated with specific TX receptor blockade. Further clinical studies will be required to confirm the provocative animal studies, as well as defining the role of TX as a mediator of coronary vasospasm, respiratory disorders, and renal failure and rejection episodes.

The purpose of this study was to examine the dose response to a highly purified human recombinant tumor necrosis factor (TNF alpha) preparation (1-2 x 10(7) U/mg; less than 0.05 ng endotoxin/mg TNF alpha) in the conscious rat. Rats received intravenous bolus injections of 0.3 mg/kg (n = 6), 1.0 mg/kg (n = 17), 3.0 mg/kg (n = 11), or 10 mg/kg (n = 15) of TNF alpha, 30 mg/kg (n = 7) Salmonella enteritidis endotoxin (LPS), or isotonic saline (n = 11). Upon termination of the experiment, the lungs were removed for lavage or histology. Survival was 0% 24 hr after the injection of LPS and 83, 59, 73, and 73% after the lowest to highest doses of TNF alpha, respectively. As with endotoxin, TNF alpha caused a dose-dependent increase in heart rate (HR) (P less than 0.05) within 0.5 hr of administration, which remained elevated throughout the 24 hr period. TNF alpha had no effect on mean arterial blood pressure (MABP) acutely, but it caused a 15-20% decrease in MABP 24 hr post exposure (P less than 0.05). TNF alpha increased hematocrit within 0.5 to 3 hr in all dose groups by 10-15%. Furthermore, TNF alpha produced a thrombocytopenia in all dose groups, although the decrease in platelet count was less than that produced by endotoxin. TNF alpha doses of 1-10 mg/kg caused leukopenia within 0.5 hr (P less than 0.05). Lavage and histology revealed no changes in the number of pulmonary neutrophils. These results suggest that TNF alpha stimulated dose-dependent responses, which were consistent with those produced by LPS. However, these responses to TNF alpha were appreciably smaller than those reported for either LPS or for TNF alpha from other sources.

Endotoxemia is associated with increases in a number of humoral mediators including vasopressin, thromboxane and leukotrienes (LT), all of which may participate in the pathophysiologic responses to endotoxemia. Previous studies from our laboratory demonstrated that endotoxin-induced hemoconcentration was attenuated with a peptidoleukotriene receptor antagonist, SK & F 104353. The purpose of this study was to investigate further the mechanism of endotoxin-induced hemoconcentration. Injection of LTD4 (51 nmol/kg, i.v.) produced an increase in the hematocrit of conscious male Sprague-Dawley rats: administration of SK & F 104353 (2 mg/kg, i.v. + 10 mg/kg/h, i.v. infusion) blocked completely this response to exogenous LTD4. Injection of Salmonella enteritidis endotoxin (30 mg/kg, i.v.) increased the hematocrit from 41 +/- 1 vol% to 55 +/- 1 vol%. Following pretreatment with SK & F 104353 (2 mg/kg, i.v. + 10 mg/kg/h, i.v.), the hemoconcentration was attenuated to 46 +/- 1 vol% (p less than 0.01). Simultaneous determination of plasma drug concentrations over a range of doses indicated that inhibition of the hemoconcentration produced by SK & F 104353 was concentration-dependent (IC30 = 0.5 microgram/ml). The IC30 for the stereoisomer, SK & F 104373, was 50 micrograms/ml. The 5-lipoxygenase/cyclooxygenase inhibitors, SK & F 86002 and BW 775C, also attenuated the endotoxin-induced increase in hematocrit, whereas indomethacin, heparin, daltroban, or the selective V1 vasopressin receptor antagonist [d(CH2)5Tyr(Me)]AVP did not significantly affect the endotoxin-induced hemoconcentration. The endotoxin-induced hemoconcentration was inhibited in a concentration-dependent, stereoselective manner with a peptidoleukotriene receptor antagonist, and by 5-lipoxygenase inhibitors, indicating that this response is mediated by peptidoleukotrienes.

Fluribiprofen, a non steroidal anti-inflammatory agent, was studied in anesthetized cats subjected to acute myocardial ischemia. Flurbiprofen was given at 0.25, 1 or 4 mg/kg bolus intravenously at 0.5 hours and again at 2.5 hours. Assessment of ischemic myocardial preservation was appraised by measurement of S-T segment elevation, and plasma and cardiac tissue creatine phosphokinase (CK) specific activity. Plasma thromboxane B2 (TB2) concentrations measured by specific radioimmunoassay for TB2, and arachidonic-induced platelet aggregation were also assessed. All three doses of flurbiprofen prevented both the increase to plasma TB2 concentrations occuring in MI (p less than 0.05) at 2, 3 and 4 hours) and platelet aggregation induced by arachidonic acid. However, flurbiprofen at either 0.25 or 4 mg/kg failed to prevent the increase in the S-T segment, the increase in plasma CK activity and failed to maintain myocardial CK values in the ischemic region. At 1 mg/kg, flurbiprofen returned S-T segment to normal values and preserved myocardial CK activities but only slightly prevented the increase in plasma CK activity. These data suggest that the low and high dose of flurbiprofen showed no protection during acute myocardial ischemia, while the intermediate dose was effective. The reason for the narrow range of myocardial preservation is not clear.

Thromboxane (TX) A2 and the prostaglandin endoperoxides, PGG2 and PGH2, have a number of biological activities including contraction of vascular and bronchial smooth muscle, platelet secretion and aggregation, and lysis of cellular membranes. Activation of TXA2 receptors may have deleterious consequences in various pathophysiologies, including coronary thrombosis, myocardial infarction, hypertension and renal injury. In addition to cyclooxygenase inhibitors, TX receptor antagonists and TX synthase inhibitors are available as specific pharmacological tools to investigate the specific involvement of TXA2 and the prostaglandin endoperoxides in these conditions. Recent reports indicate that these agents may be useful to prevent coronary artery thrombosis, prevent coronary artery reocclusion following thrombolytic therapy, attenuate the sequelae of circulatory shock, and improve kidney function after renal injury. This review will discuss the specific involvement of TX in these disorders, and compare the efficacy of different pharmacological approaches to the manipulation of either TX formation or activity.

The purpose of this study was to examine the effects of PGI2 and iloprost, a prostacyclin analog, on the sequelae of experimental endotoxic shock. Endotoxemia was produced in rats by IV injection of 20 mg/kg Salmonella enteritidis (LPS). Mean arterial blood pressure fell from 117 +/- 5 mmHg (N = 22) to 92 +/- 5 mmHg and 71 +/- 10 mmHg at 30 and 180 min post-LPS, respectively. In LPS vehicle-treated rats, blood glucose levels fell from 100 +/- 10 mg/dl to 36 +/- 8 mg/dl at 180 min. Plasma glutamate-oxaloacetate transaminase and lactate dehydrogenase (liver fraction) activities were significantly elevated above concentrations in nonshocked animals, increasing to 426 +/- 86 IU/ml and 1,019 +/- 339 IU/ml, respectively. Infusion of PGI2 or iloprost (0.5 micrograms/kg/min) did not alter the blood pressure response to LPS compared to vehicle controls. PGI2 significantly prevented the LPS-induced hypoglycemia while neither treatment significantly reduced the elevations in plasma enzymes nor prevented the lethality of LPS. Thus, the hemodynamic and biochemical indices of shock severity were not significantly improved by either prostacyclin or iloprost. It is suggested that the beneficial effects of PGI2 or prostacyclin analogs observed in other species during endotoxemia does not extend to the rat.

The mechanism of carbocyclic thromboxane A2 (CTA2) vasoconstriction was studied in thoracic aortic strips and isolated perfused cat coronary arteries. CTA2, a stable thromboxane analog, produced coronary constriction at 50 pg/ml or greater. At constant flow, 5 ng/ml CTA2 increased perfusion pressure 40 +/- 4 mmHg. The calcium antagonist nifedipine reduced CTA2-induced vasoconstriction by 8% at 1 ng/ml (NS), 22% at 10 ng/ml (NS), 65% at 100 ng/ml (P less than 0.01), and 75% at 1,000 ng/ml (P less than 0.005). Other calcium antagonists also significantly reduced CTA2-induced coronary constriction. Inhibition of vasoconstriction by calcium antagonists was not due to direct thromboxane-receptor antagonism, inasmuch as nifedipine did not prevent CTA2-induced contraction in cat aortas, vessels that are not dependent on external calcium for contraction. Reducing external Ca2+ concentration to 0.63 mM significantly reduced coronary constriction over most of the CTA2 concentration-response range. Phentolamine (1-50 micrograms/ml), phenoxybenzamine (1-100 micrograms/ml), and saralasin (0.1-10 micrograms/ml) were all without significant effect on CTA2-induced coronary constriction. The results indicate that the mechanism of thromboxane coronary vasoconstriction is by a specific thromboxane receptor that is dependent on an inward calcium flux. The data also suggest that the efficacy of calcium antagonists in coronary vasospasm may be related to their ability to noncompetitively inhibit thromboxane-induced vasoconstriction.

Leukotriene D4 (0.17-17 nmol/kg i.v.) produced a dose-dependent increase in blood pressure in the conscious rat. Infusion of the selective peptidoleukotriene receptor antagonist, SK&F 104353, produced dose-dependent shifts in the leukotriene D4 dose-response curve. However, SK&F 104353 at doses of 0.2 mg/kg + 1 mg/kg per h or 1 mg/kg + 3 mg/kg per h produced similar dose ratios of 9.2 +/- 1.1 and 9.2 +/- 1.6, respectively. The peptidoleukotriene receptor antagonist, ICI 198615, also shifted the LTD4 dose-response curve, although doses of 0.2 mg/kg + 1 mg/kg per h, 1 mg/kg + 3 mg/kg per h or 2 mg/kg + 10 mg/kg per h produced similar dose ratios of 15.7 +/- 3.4, 19.1 +/- 6.3 and 16.2 +/- 3.6, respectively. The similarity in the dose ratios observed despite increasing doses of either SK&F 104353 or ICI 198615 suggests the existence of two vascular leukotriene D4 receptor subpopulations, differentiated by high and low agonist affinity.

The purpose of these experiments was to investigate the effects of the selective peptidoleukotriene receptor antagonist, SK&F 104353, on leukotriene (LT)C4, LTD4 and LTE4 vasopressor responses in conscious, normotensive rats. Steady-state plasma concentrations of SK&F 104353 at infusion rates of 0.2 mg/kg + 1 mg/kg/hr, 1 mg/kg + 3 mg/kg/hr or 2 mg/kg + 10 mg/kg/hr were 0.5, 1.6 and 9.4 micrograms/ml, respectively, indicating that the plasma concentrations of SK&F 104353 were related directly to the infusion rate. LTC4, LTD4 and LTE4 (0.17-170 nmol/kg i.v.) produced dose-dependent increases in mean blood pressure. The ED20 dose (i.e., dose required to increase blood pressure 20 mm Hg) of LTC4, LTD4 or LTE4 was 2.7 +/- 0.4, 2.2 +/- 0.3 and 109 +/- 17 nmol/kg, respectively. SK&F 104353 produced dose-dependent, parallel shifts to the right in the LTC4 dose-response curve. Administration of SK&F 104353 at doses of 0.2 mg/kg + 1 mg/kg/hr, 1 mg/kg + 3 mg/kg/hr or 2 mg/kg + 10 mg/kg/hr produced dose ratios (i.e., ratio of ED20 in presence of SK&F 104353 to that of the vehicle group) of 6, 12 and 26, respectively. Against LTD4 responses, SK&F 104353 at doses of 0.1 mg/kg + 0.3 mg/kg/hr or 0.2 mg/kg + 1 mg/kg/hr produced dose ratios of 3 and 9, respectively. At a dose of 1 mg/kg + 3 mg/kg/hr, there was no further increase in the dose ratio, whereas a dose of 2 mg/kg + 10 mg/kg/hr resulted in a dose ratio of greater than 100.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study was designed to determine whether platelets transfer arachidonic acid or prostaglandin endoperoxide intermediates to macrophages which may be further metabolized into cyclooxygenase products. Adherent peritoneal macrophages were prepared from rats fed either a control diet or an essential fatty acid-deficient diet, and incubated with a suspension of washed rat platelets. Macrophage cyclooxygenase metabolism was inhibited by aspirin. In the presence of a thromboxane synthetase inhibitor, 7-(1-imidazolyl)heptanoic acid, immunoreactive 6-ketoprostaglandin F1 alpha formation was significantly increased 3-fold. Since this increase was greater (P less than 0.01) than that seen with either 7-(1-imidazolyl)heptanoic acid-treated platelets or aspirin-treated macrophages alone, these results indicate that shunting of endoperoxide from platelets to macrophages may have occurred. In further experiments, macrophages from essential fatty acid-deficient rats were substituted for normal macrophages. Essential fatty acid-deficient macrophages, depleted of arachidonic acid, produced only 2% of the amount of eicosanoids compared to macrophages from control rats. When platelets were exposed to aspirin, stimulated with thrombin, and added to essential fatty acid-deficient macrophages, significantly more immunoreactive 6-ketoprostaglandin F1 alpha was formed than in the absence of platelets. This increased macrophage immunoreactive 6-ketoprostaglandin F1 alpha synthesis, therefore, must have occurred from platelet-derived arachidonic acid. These data indicate that in vitro, in the presence of an inhibition of thromboxane synthetase, prostaglandin endoperoxides, as well as arachidonic acid, may be transferred between these two cell types.

A number of thromboxane (Tx) synthetase inhibitors have been found to prevent thromboxane release in acute cardiopulmonary disorders. However, little is known about Tx receptor antagonism by these substances. Imidazole, UK-37,248 and pinane thromboxane A2 (PTA2) were tested in isolated perfused cat coronary arteries, spirally cut rabbit pulmonary artery strips, and in rabbit and cat platelets for their ability to antagonize vasoconstrictor and aggregatory effects of a stable Tx agonist, carbocyclic thromboxane A2 (CTA2). Imidazole, at concentrations that completely inhibit thromboxane synthesis, failed to antagonize the vasoconstrictor effects of CTA2 in both systems. UK-37,248, at 10 to 1000 micrograms/ml, failed to inhibit CTA2-induced coronary constriction but at 1 microgram/ml reduced rabbit pulmonary artery constriction by 80 +/- 8% (P less than 0.0005). In comparison, 1 micro M PTA2 completely prevented PTA2-induced constriction in both coronary and pulmonary arteries. PTA2 did not antagonize KCl and angiotensin II responses. In platelets, PTA2 but not UK-37,248 prevented arachidonate induced aggregation in rabbit and cat platelets. Some of the beneficial effects of thromboxane synthetase inhibitors may be associated with thromboxane receptor antagonism. Inhibitors structurally similar to TxA2 appear to have greater thromboxane receptor antagonistic activity. This additional activity may be of importance in therapeutics of coronary and pulmonary disorders.

The present study was designed to examine the effects of a new organic nitrate, teopranitol, in acute myocardial ischaemia. Adult cats were subjected to 5 h of myocardial ischaemia by permanent ligation of the left anterior descending coronary artery (LAD). Teopranitol (10 mg kg-1 X h) or physiological saline (vehicle) was infused i.v., beginning 30 min after LAD occlusion and continued until the end of the experiment. All animals subjected to myocardial ischaemia showed a significant elevation of the ST-segment within 20 min of LAD occlusion. In the LAD-vehicle group, the ST-segment elevation continued to increase; teopranitol attenuated this increase and significantly reduced the ST-segment elevation at 4 and 5 h (P less than 0.05). The loss of creatine phosphokinase-specific activity from the ischaemic myocardium was significantly reduced by teopranitol (P less than 0.05), indicating an improved preservation of myocardial tissue. There was a significant initial reduction in mean arterial blood pressure by teopranitol in sham-operated cats but no consistent change of this parameter, heart rate or the computed pressure-rate product in LAD-occluded cats. Teopranitol did completely reverse the ischaemia induced formation of platelet aggregates at 1 to 5 h (P less than 0.05). It is concluded that teopranitol exerts a significant protective effect in acute myocardial ischaemia in vivo that is independent of changes in systemic haemodynamics and might be associated with the generation of an antiplatelet activity in vivo.

The following studies were designed to evaluate the efficacy of a potent and selective AVP V1 receptor antagonist ([1-beta-mercapto-beta, beta-cyçlopentamethyleneproprionic acid, 2-(O-methyl)tyrosine-8-arginine vasopressin]; AVPRA) in limiting the sequelae of endotoxemia. At 0.5 and 1.0 hr after intravenous injection of 30 mg/kg S. enteritis endotoxin (LPS) to male Sprague-Dawley rats, AVP plasma concentrations were increased to 171 +/- 20 and 100 +/- 24 pg/ml, respectively, and were significantly greater than the vehicle control values of 1 pg/ml. Injection of LPS was accompanied by the following: a decreased survival rate (20%) with a mean survival time of 21.6 +/- 6 hr (n = 10), an increased heart rate (+ 84 +/- 22 bpm), a reduced circulating platelet count (23% of initial), and an acute hemoconcentration that was maximal at 30 min after injection of LPS. In a separate group of conscious rats, it was determined that AVPRA (1-100 mg/kg/hr) produced a dose-dependent, parallel and rightward shift in the AVP vasopressor dose-response curve: the highest dose of AVPRA (i.e., 100 micrograms/kg/hr) produced approximately a 1,000-fold shift in the AVP dose-response curve. Administration of AVPRA (1-100 micrograms/kg/hr) beginning 15 min prior to the injection of LPS and continuing for 6 hr did not significantly limit any of the sequelae produced by endotoxemia. These results suggest that, in this model, acute administration of a potent V1 AVP antagonist (AVPRA) is not sufficient to prevent the cardiovascular sequelae and mortality associated with endotoxemia.

To determine if inhibition of a rabbit aorta contracting substance (RCS) corresponds to inhibition of thromboxane synthetase human washed platelets were stimulated with thrombin. RCS formation was bioassayed on rabbit aorta strips in Tyrode solution containing selective blocking agents and thromboxane (TX)B2 in the same probes by specific radioimmunoassay. Dazoxiben inhibited the formation of TXB2 but not of RCS, whereas indomethacin inhibited both RCS and TX formation. The data indicate that the rabbit aorta cannot be used alone to predict inhibition of TX formation with specific TX synthetase inhibitors.

The purpose of this study was to examine the effects of the thromboxane receptor antagonist, BM 13.505, on the responses to endotoxemia in the conscious rat. The pharmacodynamics of BM 13.505 (30 mg/kg, i.v.) were first determined by pretreating male Sprague-Dawley rats 5 min, 24 h or 48 h prior to an LD90 dose of the thromboxane mimetic U 46619. Administration of a single dose of BM 13.505 5 min or 24 h prior to the challenge with U 46619 protected completely against sudden death (100% survival, p less than 0.01), while injection of BM 13.505 48 h prior to the U 46619 challenge did not protect against death. In a separate group of conscious rats, endotoxemia (30 mg/kg i.v. Salmonella enteritidis endotoxin) produced a decrease in the number of circulating platelets to 45 +/- 4% and 20 +/- 4% of the initial value at 1 and 6 h, respectively. The number of circulating white blood cells was reduced to 21 +/- 4% of the initial value at 1 h and returned to 68 +/- 9% of the initial value at 6 h. Survival following endotoxin administration was 44% at 48 h. In endotoxemic animals pretreated with BM 13.505 (30 mg/kg, i.v.), the endotoxin-induced thrombocytopenia was significantly attenuated (p less than 0.05), but there was no effect on either the endotoxin-induced early leukopenia or late leukocytosis. Survival in the BM 13.505-treated endotoxemic group was 31% at 48 h (p greater than 0.05, compared to the endotoxin + vehicle group).(ABSTRACT TRUNCATED AT 250 WORDS)

The omega-6 and omega-9 hydroperoxides of arachidonic acid (AA) caused dose-dependent contraction of rabbit aortic strip (RAS) and guinea pig ileum (GPI) at concentrations between 5 and 200 microM. At these concentrations, arachidonic acid had no effect in these preparations. The contractions could not be blocked by indomethacin, methysergide, phenoxybenzamine, propranolol, diphenhydramine, scopolamine, or the SRS-A antagonist FPL-55712, but were abolished by the calcium channel blocker nimodipine. In both tissues, the hydroperoxides initiated a sustained contraction. The onset of GPI contraction however, was much faster than the response of RAS to these hydroperoxides. 15-HPETE produced a more sustained contraction than 12-HPETE in both RAS and GPI. These results suggest that hydroperoxides generated from AA by the action of lipoxygenase can directly induce smooth muscle contraction and this effect is probably mediated through altering calcium fluxes in these smooth muscle preparations.

LG 82-4-00 (5-(2-(1-imidazolyl)-ethoxy)-thiophene-2-carboxylate) and LG 82-4-01 (4-chloro-thiophenic-substituted derivative) were examined for specific inhibition of thromboxane (TX) synthetase. Thromboxane formation was measured by a radioimmunoassay specific for TXB2. In thrombin (0.6 IU/ml)-stimulated, washed human platelet suspensions (WPS) the IC50 (microM) for inhibition of TX formation were 1.1 (LG 82-4-00), 1.3 (LG 82-4-01) and 0.7 (dazoxiben). LG 82-4-00, LG 82-4-01 and dazoxiben also inhibited collagen (0.6-2.5 micrograms/ml)-induced TXB2 formation and platelet aggregation in human platelet-rich plasma. Neither LG 82-4-00 nor LG 82-4-01 had vasoconstrictor, proaggregatory or TX antagonistic activity or affected primary wave ADP aggregation. There was less than 10% inhibition of PGI2 formation from bovine coronary artery slices with concentrations up to 100 microM. At 100 microM, dazoxiben inhibited thrombin-induced 12-HPETE formation in WPS by 81 +/- 10% whereas LG 82-4-00 and LG 82-4-01 were much less active. These data indicate that LG 82-4-00 and LG 82-4-01 are specific inhibitors of thromboxane synthetase in human platelets.