Inhibition of antigen-induced arthritis in guinea pigs by a selective LTB4 receptor antagonist LY293111Na

OBJECTIVE AND DESIGN

To investigate the role of leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) in the development and progression of antigen-induced arthritis (AIA) in guinea pigs and rats.

METHODS

Arthritis was induced by injecting cationic amidated bovine serum albumin (aBSA) into the knee joint of immunized guinea pigs or rats. The effect of a potent and selective LTB4 receptor antagonist, LY29311INa (2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]-propoxy]-phenoxy]benzoic acid sodium salt) was compared with those of indomethacin and dexamethasone. The effect of LY293111Na on adjuvant arthritis in rats was also examined.

RESULTS

LY293 111Na (5 to 50 mg/kg b.i.d.) significantly inhibited knee joint swelling and histopathological changes of AIA in guinea pigs, but not in rats. Especially its protective effect against bone and cartilage destruction was substantial. In contrast, the cyclooxygenase inhibitor indomethacin significantly inhibited AIA in rats, but slightly inhibited in guinea pigs, while dexamethasone markedly inhibited AIA in both guinea pigs and rats. Increases of LTB4 and myeloperoxidase (MPO) activity were observed in the knee joint tissue of AIA guinea pigs, and LY293111Na dose-dependently inhibited the increase of MPO activity. Moreover, in adjuvant arthritic rats, LY293111Na showed slight inhibitory effect, while indomethacin showed marked inhibition.

CONCLUSIONS

LTB4 but not PGE2 appeared to play important roles as an effective mediator in joint, particularly in cartilage and bone destruction of AIA in guinea pigs probably by inducing polymorphonuclear leukocytes (PMNs) chemotaxis to the joint tissue. In contrast, PGE2 but not LTB4 is an important mediator of arthritis in rats.

Effects of leukotriene B4 receptor antagonist, LY293111Na, on antigen-induced bronchial hyperresponsiveness and leukocyte infiltration in sensitized guinea pigs

OBJECTIVE AND DESIGN

LY29311 Na, 2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy] propoxy] -phenoxy]-benzoic acid sodium salt, is a novel leukotriene B4 (LTB4) receptor antagonist. Its effects on guinea pig models of asthma were compared with those of dexamethasone.

METHODS

Effects of LY293111Na were tested in antigen (ovalbumin, OA)-induced bronchial hyperresponsiveness (BHR) and leukocyte accumulation in actively sensitized guinea pigs. Its effects on antigen-induced acute bronchoconstriction in passively sensitized guinea pigs were also studied.

RESULTS

LY293111 Na (10 to 30 mg/kg p.o., 1 h before and 6 h after OA challenge) inhibited BHR to acetylcholine. LY293111 Na (3 mg/kg p. o.) significantly inhibited accumulation of neutrophils in bronchoalveolar lavage (BAL) fluid 24 h after antigen challenge but it did not inhibit accumulation of eosinophils and macrophages at any doses used. In contrast, dexamethasone (30 mg/kg p.o., 4 h before OA challenge) not only inhibited BHR but also reduced the infiltration of all three types of leukocytes. A significant increase of LTB4 levels in BAL fluid was noted at 3 and 15 min after the antigen challenge. LY293111Na did not inhibit antigen-induced acute bronchoconstriction in passively sensitized guinea pigs.

CONCLUSION

These results indicate that LTB4 may participate in antigen-induced BHR but not in eosinophil infiltration and acute bronchoconstriction in guinea pigs.

LY393615, a novel neuronal Ca(2+) and Na(+) channel blocker with neuroprotective effects in models of in vitro and in vivo cerebral ischemia

In the present studies we have examined the effects of a new calcium channel blocker, LY393615 ((N-Butyl-[5,5-bis-(4-fluorophenyl)tetrahydrofuran-2-yl]methylamine hydrochloride, NCC1048) in a model of hypoxia-hypoglycaemia in vitro and in a gerbil model of global and in two rat models of focal cerebral ischaemia in vivo. Results indicated that LY393615 protected against hypoxia-hypoglycaemic insults in brain slices and also provided significant protection against ischaemia-induced hippocampal damage in gerbil global cerebral ischaemia when dosed at 10, 12.5 (P<0.05) or 15 mg/kg i.p. (P<0.01) 30 min before and 2 h 30 min after occlusion. The compound penetrated the brain well after a 15 mg/kg i.p. dose and had a half-life of 2.5 h. In further studies LY393615 was protective 1 h post-occlusion when administered at 15 mg/kg i.p. followed by 2 doses of 5 mg/kg i.p. 2 and 3 h later. LY393615 dosed at 15 mg/kg i.p. followed by 2 further doses of 5 mg/kg i.p. (2 and 3 h later) also produced a significant reduction in the infarct volume following Endothelin-1 (Et-1) middle cerebral artery occlusion in the rat when administration was initiated immediately (P<0.01) or 1 h (P<0.05) after occlusion. The compound was also evaluated in the intraluminal monofilament model of focal ischaemia. The animals had the middle cerebral artery occluded for 2 h, and 15 min after reperfusion LY393615 was administered at 15 mg/kg i.p. followed by 2 mg/kg/h i.v. infusion for 6 h. There was no reduction in infarct volume using this dosing protocol. In conclusion, in the present studies we have reported that a novel calcium channel blocker, LY393615, with good bioavailability protects against neuronal damage caused by hypoxia-hypoglycaemia in vitro and both global and focal cerebral ischaemia in vivo. The compound is neuroprotective when administered post-occlusion and may therefore be a useful anti-ischaemic agent.

Effects of the second-generation leukotriene B(4) receptor antagonist, LY293111Na, on leukocyte infiltration and collagen-induced arthritis in mice

The effects of the second-generation leukotriene B(4) receptor (LTB(4) receptor) antagonist, 2-[2-propyl-3-¿3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxy-phenoxy]-propo xy¿phenoxy]benzoic acid sodium salt (LY293111Na), on leukotriene B(4)-induced leukocyte infiltration and interleukin-1-accelerated collagen-induced arthritis in mice were studied. Neutrophil infiltration induced into an air pouch by leukotriene B(4) was dose-dependently inhibited by LY293111Na and strongly so by another LTB(4) receptor antagonist, 4-[5-¿4-(aminoiminomethyl)phenoxy¿pentoxy]-3-methoxy-N, N-bis(1-methylethyl) (Z)-2butenedioate (1:1) (CGS25019C). Both compounds significantly inhibited the increase of the arthritis index and the ankle bone destruction in interleukin-1-accelerated collagen-induced arthritis. Phenidone, a 5-lipoxygenase inhibitor, also inhibited interleukin-1-accelerated collagen-induced arthritis, while indomethacin and tenidap, cyclooxygenase inhibitors, had slight inhibitory effects. Injection of interleukin-1 elicited a marked increase of the leukotriene B(4) level in arthritic paws, while the prostaglandin E(2) level was slightly increased. These findings indicate clearly that leukotriene B(4) is an important mediator of interleukin-1-accelerated collagen-induced arthritis in mice. If this can be extrapolated to man, LTB(4) receptor antagonists might be useful for treatment of the acute progressive phase of human arthritis.

ARL 17477, a selective nitric oxide synthase inhibitor, with neuroprotective effects in animal models of global and focal cerebral ischaemia

In the present studies, we have evaluated the effects of N-[4-(2-¿[(3-Chlorophenyl)methyl]amino¿ethyl)phenyl]-2-thiophenecarbo ximidamide dihydrochloride (ARL 17477) on recombinant human neuronal NOS (nNOS) and endothelial NOS (eNOS). We then carried out pharmacokinetic studies and measured cortical nitric oxide synthase (NOS) inhibition to determine that the compound crossed the blood brain barrier. Finally, the compound was evaluated in a model of global ischaemia in the gerbil and two models of transient focal ischaemia in the rat. The IC(50) values for ARL 17477 on human recombinant human nNOS and eNOS were 1 and 17 microM, respectively. ARL 17477 (50 mg/kg i.p.) produced a significant reduction in the ischaemia-induced hippocampal damage following global ischaemia when administered immediately post-occlusion, but failed to protect when administration was delayed until 30 min post-occlusion. In the endothelin-1 model of focal ischaemia, ARL 17477 (1 mg/kg i.v.) significantly attenuated the infarct volume when administered at either 0, 1 or 2 h post-endothelin-1 (P<0.05). In the intraluminal suture model, ARL 17477 at both 1 and 3 mg/kg i.v. failed to reduce the infarct volume measured at 1, 3 or 7 days post-occlusion. These results demonstrate that ARL 17477 protects against global ischaemia in gerbils and provides some reduction in infarct volume following transient middle cerebral artery occlusion in rats, indicating that nNOS inhibition may be a useful treatment of ischaemic conditions.

Pharmacology of LY315920/S-5920, [[3-(aminooxoacetyl)-2-ethyl-1- (phenylmethyl)-1H-indol-4-yl]oxy] acetate, a potent and selective secretory phospholipase A2 inhibitor: A new class of anti-inflammatory drugs, SPI

LY315920 is a potent, selective inhibitor of recombinant human, group IIA, nonpancreatic secretory PLA2 (sPLA2). In a chromogenic isolated enzyme assay, LY315920 inhibited sPLA2 activity with an IC50 of 9 +/- 1 nM or 7.3 x 10(-6) mole fraction, which approached the stiochiometric limit of this assay. The true potency of LY315920 was defined using a deoxycholate/phosphatidylcholine assay with a mole fraction of 1.5 x 10(-6). LY315920 was 40-fold less active against human, group IB, pancreatic sPLA2 and was inactive against cytosolic PLA2 and the constitutive and inducible forms of cyclooxygenase. Human sPLA2-induced release of thromboxane A2 (TXA2) from isolated guinea pig lung bronchoalveolar lavage cells was inhibited by LY315920 with an IC50 of 0.79 microM. The release of TXA2 from these cells by N-formyl-methionyl-leucyl-phenylalanine or arachidonic acid was not inhibited. The i.v. administration of LY315920, 5 min before harvesting the bronchoalveolar lavage cells, resulted in the inhibition of sPLA2-induced production of TXA2 with an ED50 of 16.1 mg/kg. Challenge of guinea pig lung pleural strips with sPLA2 produced contractile responses that were suppressed in a concentration-dependent manner by LY315920 with an apparent KB of 83 +/- 14 nM. Contractile responses induced by arachidonic acid were not altered. Intravenous or oral administration of LY315920 to transgenic mice expressing the human sPLA2 protein inhibited serum sPLA2 activity in a dose-related manner over a 4-h time course. LY315920 is a potent and selective sPLA2 inhibitor and represents a new class of anti-inflammatory agent designated SPI. This agent is currently undergoing clinical evaluation and should help to define the role of sPLA2 in various inflammatory disease states.

Pharmacologic actions of the second-generation leukotriene B4 receptor antagonist LY293111: in vitro studies

The in vitro actions were investigated of LY293111, a potent and selective leukotriene B4 (LTB4) receptor antagonist, on human neutrophils, human blood fractions, guinea pig lung membranes, and guinea pig parenchymal and tracheal strips. The IC50 for inhibiting [3H]LTB4 binding to human neutrophils was 17.6 +/- 4.8 nM. LY293111 inhibited LTB4-induced human neutrophil aggregation (IC50 = 32 +/- 5 nM), luminol-dependent chemiluminescence (IC50 = 20 +/- 2 nM), chemotaxis (IC50 = 6.3 +/- 1.7 nM), and superoxide production by adherent cells (IC50 = 0.5 nM). Corresponding responses induced by N-formyl-L-methionyl-L-leucyl-L-phenylalanine were inhibited by 100-fold higher concentrations of LY293111. LTB4 binding to guinea pig tissues and subsequent activation were also inhibited. The Ki for inhibition of [3H]LTB4 binding to lung membranes was 7.1 +/- 0.8 nM; IC50 for preventing binding of [3H]LTB4 to spleen membranes was 65 nM. The compound inhibited LTB4-induced contraction of guinea pig lung parenchyma. At 10 nM, LY293111 caused a parallel rightward shift of the LTB4 concentration-response curve. At higher concentrations, plots were shifted in a nonparallel manner, and maximum responses were depressed. LY293111 did not prevent antigen-stimulated contraction of sensitized trachea strips. At micromolar concentrations, LY293111 inhibited production of LTB4 and thromboxane B2 by plasma-depleted human blood stimulated with N-formyl-L-methionyl-L-leucyl-L-phenylalanine and thrombin. In addition, at these higher concentrations, formation of LTB4 by A23187-activated whole blood and conversion of arachidonic acid to LTB4 by a human neutrophil cytosolic fraction were inhibited. In summary, LY293111 is a second-generation LTB4 receptor antagonist with much improved potency in a variety of functional assay systems.

Recombinant human secretory phospholipase A2 released thromboxane from guinea pig bronchoalveolar lavage cells: in vitro and ex vivo evaluation of a novel secretory phospholipase A2 inhibitor

The primary objective of this study was to develop a functional assay that could provide rapid and reliable information on some pharmacologic characteristics of a novel inhibitor of human secretory phospholipase A2 (sPLA2). Guinea pig bronchoalveolar lavage (BAL) fluid, containing predominantly macrophages, eosinophils and epithelial cells, released thromboxane A2, as measured by thromboxane B2, in a concentration-dependent manner on exposure to recombinant human sPLA2 (rh-sPLA2). Similarly, n-formyl-L-methionyl-L-leucyl-L-phenylalanine (n-F-Met-Leu-Phe) or arachidonic acid also released this lipid mediator. Indomethacin, a cyclooxygenase inhibitor, blocked synthesis of thromboxane in response to these agents. p-Bromophenacylbromide-inactivated rh-sPLA2 was substantially less effective than the untreated enzyme in causing release of thromboxane. LY311727 is a potent indole-derived inhibitor of the isolated enzyme (IC50 = 23 nM). Incubation of this agent with BAL cells, just before addition of rh-sPLA2, reduced release of thromboxane with an IC50 = 1.8 x 10(-6) M. Specificity for sPLA2 was demonstrated in that LY311727, unlike indomethacin, did not reduce synthesis and subsequent release of thromboxane A2 in response to arachidonic acid. Using this technique as a basis, we determined whether LY311727 could sufficiently accumulate in lung after i.v. administration to inhibit rh-sPLA2-induced thromboxane A2 release from BAL cells. The compound, given i.v. to guinea pigs 5 min before collecting BAL fluid, produced a dose-dependent inhibition of rh-sPLA2 with an ED50 = 50 mg/kg. Thus, new in vitro and ex vivo assays were developed that permit functional evaluation of novel sPLA2 inhibitors. These techniques should serve as secondary assays for evaluation of human sPLA2 inhibitory activity from a chemical series and in addition provide initial data related to metabolic stability and distribution to the lung.

Synthetic and structure/activity studies on acid-substituted 2-arylphenols: discovery of 2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5- hydroxyphenoxy]-propoxy]phenoxy]benzoic acid, a high-affinity leukotriene B4 receptor antagonist

Structural derivatives of LY255283 have been studied as receptor antagonists of leukotriene B4. Substitution of the 2-hydroxyacetophenone subunit of 1 (LY255283) with a 2-arylphenol group provided entry into several new series that feature various mono- and diacidic core functionality. These new analogues, the subject of a broad structure-activity investigation, displayed significantly increased in vitro and in vivo activity as receptor antagonists of LTB4. A series of diaryl ether carboxylic acids demonstrated especially interesting activity and led to the discovery of compound 43b, 2-[2-propyl-3-[3-[2-ethyl-4-(4- fluorophenyl)-5-hydroxyphenoxy]-propoxy]phenoxy]benzoic acid (LY293111), a 2-arylphenol-substituted diaryl ether carboxylic acid which displayed potent binding to human neutrophils (IC50 = 17 +/- 4.6 nM) and guinea pig lung membranes (IC50 = 6.6 +/- 0.71 nM), inhibition of LTB4-induced expression of the CD11b/CD18 receptor on human neutrophils (IC50 = 3.3 +/- 0.81 nM), and inhibition of LTB4-induced contraction of guinea pig lung parenchyma (pKB = 8.7 +/- 0.16). In vivo, 43b demonstrated potent activity in inhibiting LTB4-induced airway obstruction in the guinea pig when dosed by the oral (ED50 = 0.40 mg/kg) or intravenous (ED50 = 0.014 mg/kg) routes. A specific LTB4 receptor antagonist, 43b had little effect on inhibiting contractions of guinea pig lung parenchyma induced by leukotriene D4 (LTD4), histamine, carbachol, or U46619. Compound 43b has been chosen as a clinical candidate and is currently in phase I studies for a variety of inflammatory diseases.

Differential relaxant responses of guinea-pig lung strips and bronchial rings to sodium nitroprusside: a mechanism independent of cGMP formation

The biochemical mechanism subserving smooth muscle relaxant effects of sodium nitroprusside was examined on U46619, 9,11-dideoxy-9 alpha,11 alpha-methanoepoxy PGF2 alpha, precontracted guinea-pig lung strips and hilar bronchial rings. Lung strips were resistant to the relaxant action of sodium nitroprusside or sodium nitrite (NaNO2), whereas they markedly relaxed to 8-bromo-cyclic GMP (8-Br-cGMP), a membrane permeable analogue of cGMP. Precontracted bronchial rings completely relaxed to sodium nitroprusside, NaNO2, or 8-Br-cGMP in a concentration-dependent manner. Sodium nitroprusside (10 microM) substantially raised tissue cGMP level in lung strips. Conversely, sodium nitroprusside had no detectable effect on cGMP levels in bronchial rings. In the presence of 10 microM dipyridamole, an agent which preferentially inhibits cGMP-specific phosphodiesterase, cGMP levels in lung strips treated with sodium nitroprusside was significantly enhanced, but sodium nitroprusside demonstrated no relaxant effect on the preparations. However, dipyridamole potentiated sodium nitroprusside-induced precontracted bronchial ring relaxation without affecting the bronchial tissue cGMP level. In the presence of 10 microM LY83583 (6-anilino-5,8-quinoline-dione), a specific cGMP concentration-lowering agent, sodium nitroprusside-mediated elevation of cGMP level in lung strips was significantly reduced with no effect on the functional response. LY83583 demonstrated no inhibitory effect on either relaxation or cGMP level in bronchial rings treated with sodium nitroprusside. Our results suggest that precontracted smooth muscle in lung strips and in hilar bronchi respond distinctly to sodium nitroprusside. Furthermore, sodium nitroprusside mediates bronchial smooth muscle relaxation by mechanisms unrelated to cGMP.

A novel leukotriene B4-receptor antagonist in endotoxin shock: a prospective, controlled trial in a porcine model

OBJECTIVE

To evaluate the hypothesis that treatment with LY255283, a novel leukotriene B4-receptor antagonist, is beneficial in an animal model of the adult respiratory distress syndrome induced by endotoxin.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Laboratory at a large university medical center.

SUBJECTS

Twenty-five, immature, random-bred swine.

INTERVENTIONS

Four groups of pigs were studied: the LPS group of animals (n = 6) were infused with Escherichia coli lipopolysaccharide (strain 0111:B4, 250 micrograms/kg) from 0 to 60 mins; the LPS + 255283 group of animals (n = 6) were infused with lipopolysaccharide as above, but were also treated with LY255283 (30 mg/kg, then 10 mg/kg/hr), beginning at -15 mins; the 255283 group of animals (n = 6) were infused with the same dose of LY255283, but were not challenged with lipopolysaccharide; and the RL control group of subjects (n = 7) received only the lactated Ringer's solution vehicle. Beginning at 30 mins, all groups were infused with dextran-70 solution as needed to maintain cardiac output at 90% to 110% of baseline value.

MEASUREMENTS AND MAIN RESULTS

Treatment with LY255283 significantly (p < .05) ameliorated lipopolysaccharide-induced systemic arterial hypotension, pulmonary arterial hypertension, and arterial hypoxemia. Treatment with this drug also abrogated lipopolysaccharide-induced increases in pulmonary extravascular water content and bronchoalveolar lavage fluid protein concentration.

CONCLUSIONS

These data suggest that leukotriene B4 may be an important mediator of acute lung injury in this porcine model of septic shock and acute lung injury. Further studies to assess the specificity of LY255283 as a leukotriene B4 antagonist are necessary in order to exclude the possibility that the beneficial effects of this compound are due to pharmacologic actions other than the blockade of LTB4 receptors.

Contraction of guinea pig inferior vena cava by eicosanoids

Guinea pig inferior vena cava contracted in response to leukotriene (LT)C4, LTD4, LTE4 U46619, phenylephrine, histamine, and KCl. Although LTC4, LTD4, and U46619 were the most potent agonists, active tension generated by these eicosanoids was only about half that of histamine or KCl. LTE4 and phenylephrine were marginally active. Biochemical analysis showed vena cava able to convert about 23% LTC4 to LTD4 and LTE4 in 45 min. Pretreatment with acivicin prevented this by abrogating conversion of LTC4 to LTD4. A subthreshold concentration of LTE4 reduced responses to LTC4 and LTD4. LY171883 and WY-48252 competitively antagonized LTD4-induced contractions of vena cava. In contrast, these antagonists blocked contractions to LTC4 in a biphasic manner. Lower segments of the LTC4 concentration-response curves were less affected than the upper portion suggesting the possibility of 2 LTC4 receptor subtypes. Our results indicate that LTE4 is a weak or partial agonist in this tissue and furthermore they suggest a lack of high affinity receptors for LTE4 favoring LTC4 and LTD4. Indomethacin did not influence contractions to the leukotrienes or histamine. However, the response to U46619 was greatly enhanced suggesting release of a vasodilator prostaglandin as part of the overall response of the vena cava to the thromboxane A2 mimetic.

Pulmonary actions of LY255283, a leukotriene B4 receptor antagonist

The actions of LY255283, a leukotriene (LT) B4 receptor antagonist, were examined on guinea pig lung. LTB4 and LY255283 displaced [3H]LTB4 from its binding site on lung membranes with pKi values of 9.9 and 7.0, respectively. In the functional correlate of the binding studies, LY255283 competitively reduced contractile responses of lung parenchyma to LTB4 (pA2 = 7.2). LTB4 produced airway obstruction which was reduced by LY255283 administered i.v. (ED50 = 2.8 mg/kg) or orally (ED50 = 11.0 mg/kg). Contractile responses to histamine, LTD4 and the thromboxane mimetic, U46619, were not reduced by LY255283. The compound also did not inhibit cyclooxygenase or 5-lipoxygenase enzymes. We conclude that LY255283 selectively antagonized pharmacologic responses to LTB4 on lung tissue and appears to be a useful tool to investigate the role of LTB4 in pulmonary disease.

Contributory role of lung pleura to release of anaphylactic mediators from guinea pig lung in response to ovalbumin or A23187

Previous findings revealed greater contractile responses of guinea pig lung pleural surface strips to antigen or A23187 challenge than denuded lung parenchymal strips (lung strip devoid of any pleura). Moreover, we have identified a high density of mast cells distributed throughout the lung pleura. The present study examined mediators released from guinea pig lung pleural surface and denuded lung parenchyma fragments in response to immunologic challenge with ovalbumin (OA) or non-immunologic challenge with the ionophore A23187. Histamine levels were measured radioenzymatically; leukotrienes (LTs), prostaglandins (PGs) and thromboxane B2 (TXB2), a stable metabolite of thromboxane A2 (TXA2), were quantitated using an enzyme immunoassay. Histamine release reached a maximal level 3-5 min after OA challenge, whereas A23187-induced histamine release increased gradually in a time-dependent manner. Similar kinetics were observed in the release of LTs, PGs and TXA2. Pleural surface released a substantially (P < 0.05) greater amount of histamine to both challenges than denuded parenchyma. Moreover, histamine content in pleural surface was significantly (P < 0.05) higher than in denuded parenchyma. Pleural surface also released considerably (P < 0.05) more LTB4, LTC4, and LTE4 in response to OA and A23187 than denuded parenchyma. In contrast, pleural surface and denuded parenchyma released equivalent amounts of PGD2, PGE2, PGF2 alpha, and TXA2 in response to both challenges. The rank order of leukotriene release was LTC4 > LTE4 > LTB4, whereas that of prostanoid release was TXA2 >> PGD2 > or = PGF2 alpha >> PGE2. We conclude that pleural surface is the major source of histamine and leukotrienes released from guinea pig lung in vitro in response to OA and A23187, whereas both pleural surface and denuded parenchyma participate to the same extent in prostaglandin and TXA2 production after such challenges.

Optimization of the quinoline and substituted benzyl moieties of a series of phenyltetrazole leukotriene D4 receptor antagonists

This report describes the development of a series of highly potent quinoline-based leukotriene D4 (LTD4) receptor antagonists containing an N-benzyl-substituted phenyltetrazole moiety. They were designed to provide both the correct positioning of the acidic function and secondary lipophilic domain required for strong receptor binding. Members of this series possess high activity in blocking LTD4-induced contractions of isolated guinea pig ileum. Compound 32, LY287192 (2-[[5-[3-[2-(7-chloroquinolin-2- yl)ethenyl]phenyl]-2H-tetrazol-2-yl]methyl]-5-fluorobenzoic acid sodium salt), blocked contraction with a pKB value of 9.1 +/- 0.3. Qualitative structure-activity studies have demonstrated specific requirements for the best activity. In particular, ortho substitution of the benzyl group with an acidic function was crucial for maximum potency. In cases similar to 32, where the benzyl group possesses an ortho carboxylate, the N-2-substituted tetrazole isomer showed 100-fold greater activity relative to the corresponding N-1 isomer. This pattern was reversed when the acid was substituted at the para position. The quinoline unit may be replaced by other nitrogen-containing heterocycles.

Development of a series of phenyltetrazole leukotriene D4 (LTD4) receptor antagonists

A hypothetical model for receptor binding of leukotriene D4 (LTD4) was deduced from conformational analysis of LTD4 and from the structure-activity relationships (SAR) of known LTD4 receptor antagonists. A new structural series of LTD4 receptor antagonists exemplified by 5-[4-(4-phenylbutoxy)phenyl]-2-[4-(tetrazol-5-yl)butyl]-2H-t etrazole was designed in which a phenyltetrazole moiety was incorporated as a receptor binding equivalent of the triene unit of LTD4. A number of these phenyltetrazoles were prepared and found to possess LTD4 receptor antagonist activity. The structure-activity relationship (SAR) of this series is described.

Pharmacological and histological examinations of regional differences of guinea-pig lung: a role of pleural surface smooth muscle in lung strip contraction

1. Parenchymal lung strip preparations have been widely used as an in vitro model of peripheral airway smooth muscle. The present study examined functional responses of 4 consecutive guinea-pig lung parenchymal strips isolated from the central region (segment 1) to the distal edge (segment 4) of the lower lung lobe. The middle two segments were designated as segments 2 and 3. 2. Lung segments 1 and 4 exhibited significantly greater contraction than the other 2 segments to KCl when responses were expressed as mg force per mg tissue weight. Contractile responses to bronchospastic agents including histamine, carbachol, endothelin-1, leukotrienes (LT) B4 and D4, and the thromboxane A2-mimetic U46619 demonstrated no significant difference in EC50 values among the 4 lung segments. 3. Contractile responses of segments 1 and 4 to antigen-challenge (ovalbumin), ionophore A23187 and substance P were significantly greater than the other 2 segments with respect to either sensitivity or maximum responsiveness. 4. U46619-induced contractions of the 4 lung segments were relaxed in similar manner by papaverine and theophylline up to 100%, salbutamol up to 80%, and sodium nitroprusside by only 20%. In contrast, sodium nitroprusside markedly reversed U46619-induced contraction of pulmonary arterial rings and bronchial rings. 5. Histological studies identified 2-4 layers of smooth muscle cells underlying the lung pleural surface. Mast cells were prominent in this area. Moreover, morphometric studies showed that segment 4 possessed the least amount of smooth muscle structures from bronchial/bronchiolar wall and vasculatures as compared to the other 3 segments, and a significant difference in this respect was evident between segment 1 and segment 4.6. Since lung segments 1 and 4 are covered with larger surface area of lung pleura, the present results suggest that the significantly greater intrinsic contractile responses of segments 1 and 4 are associated with the presence of increased lung pleural surface possibly together with more mast cells. Thus, a primary contribution to the net contraction of the lung parenchymal strips may be smooth muscle from the lung pleura, alveolar ducts and interstitial contractile cells rather than from bronchi/bronchioles and microvasculatures.

Pharmacologic evaluation of A23187-induced contractions of three distinct preparations of guinea pig lung parenchymal strips

The present investigation examined the pharmacologic profiles of three distinct guinea pig lung parenchymal strips (LPS): intact LPS, denuded LPS (devoid of any lung pleura) and pleural surface strips. All three preparations responded similarly to increasing concentrations of KCl, whereas maximum contractile responses of the intact LPS and pleural surface strips to histamine, LTD4 and U46619, a thromboxane A2 mimetic, were significantly greater (P less than 0.001) than those elicited by the denuded LPS. Moreover, concentration-response curves for intact LPS and pleural surface strips to ovalbumin and ionophore A23187 challenges were equivalent to each other, which were significantly (P less than 0.001) higher in magnitude than that for the denuded LPS. The net contractile response of the denuded LPS to A23187 was significantly reduced by 35% in the presence of 1 x 10(-5) M A-64077, a 5-lipoxygenase inhibitor, and nearly abolished with the addition of 1 x 10(-6) M pyrilamine and 4 x 10(-6) M indomethacin. In contrast, the maximum contractile responses of the intact LPS and pleural surface strips were reduced by 40 and 30%, respectively, in the presence of all three inhibitors. On the other hand, morphometric analysis revealed that the density of mast cells in the smooth muscle of lung pleura was as high as that found in the bronchiolar area (2.35 +/- 0.31 vs. 2.62 +/- 0.28 per 0.05 mm2). In contrast, mast cells were scarcely identified in the alveolar parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)

(Phenylmethoxy)phenyl derivatives of omega-oxo- and omega-tetrazolylalkanoic acids and related tetrazoles. Synthesis and evaluation as leukotriene D4 receptor antagonists

Two series of (phenylmethoxy)phenyl compounds derived from the structure of LY163443 were synthesized and evaluated as leukotriene D4 receptor antagonists. In the omega-[(phenylmethoxy)phenyl]-omega-oxoalkanoic acid series, 5-[4-[(4-acetyl-2-ethyl-3-hydroxyphenyl)methoxy]phenyl]-3,3-dimethyl-5- oxopentanoic acid (8) was the most potent antagonist of LTD4-induced contractions of guinea pig ileum (pKB of 7.60) and LTD4 pressor response in pithed rats (ED50 of 1.4 mg/kg iv). Replacing the carboxylic acid function with 5-tetrazole gave slightly more potent compounds. In the omega-[5-[[(phenylmethoxy)phenyl]alkyl] tetrazolyl]alkanoic acid series, replacing the carboxylic acid with 5-tetrazole gave compounds that were equally effective in the guinea pig ileum but more potent in vivo against the LTD4 pressor response in rat. The pKB value in the guinea pig ileum for 1-[2-hydroxy-3-propyl-4- [[4-[[2-[3-(1H-tetrazol-5-yl)propyl]-2H-tetrazol-5-yl]methyl ] phenoxy]methyl]phenyl]ethanone (25) was 7.87 and the ED50 for antagonism of the LTD4 pressor response was 4.0 mg/kg iv. The sodium salts of 8 (9) and 25 (26) given by the iv route of administration antagonized LTD4-induced cardiovascular alterations in anesthetized rat and LTD4-induced bronchoconstriction in guinea pig in a dose-dependent manner. Oral activity was also demonstrated against the LTD4-induced bronchoconstriction in guinea pig.

Leukotriene receptor antagonism and augmentation of beta-receptor-mediated events by LY171883

LY171883, (1-[2-hydroxy-3-propyl-4-[4(1H-tetrazol-5-yl)butoxy)phenyl]etha none), a leukotriene (LT) D4/E4 receptor antagonist, was assessed in comparison with two well known phosphodiesterase inhibitors, isobutylmethyl-xanthine (IBMX) and theophylline, for its ability to augment beta-receptor-mediated responses. Relaxation of carbachol-contracted guinea-pig trachea by isoprenaline was enhanced by the three agents in a dose-dependent manner. A two-fold enhancement of isoprenaline-induced smooth muscle relaxation was produced by 2.5 microM IBMX, 28 microM LY171883, or 140 microM theophylline. Similar concentrations of IBMX or theophylline did not antagonize LTE4-induced tracheal contractions; LY171883 totally inhibited the response and had significant LTE4 receptor antagonist activity even at 10-fold lower concentrations. Antigen-induced release of histamine and LTC4 from guinea-pig lung was reduced by isoprenaline. Prior treatment with LY171883, IBMX, or theophylline did not enhance this action. Isoprenaline reduced histamine-induced bronchospasm in anaesthetized guinea-pigs. LY171883, 30 mg kg-1, or IBMX, 1 mg kg-1, did not affect the isoprenaline-induced decrease in the histamine response. IBMX, 3 mg kg-1, and theophylline, 30 mg kg-1, augmented the isoprenaline-induced bronchodilation. LTE4-induced bronchoconstriction was not affected by IBMX or theophylline whereas LY171883 antagonized this response at doses as low as 3 mg kg-1. Therefore, in both in-vitro and in-vivo test systems, LY171883 functioned primarily as a leukotriene receptor antagonist with minimal pharmacological activity attributable to its ability to potentiate isoprenaline.

Leukotriene (LT) receptor antagonists. Heterocycle-linked tetrazoles and carboxylic acids. LY203647

LY171883, 1-[2-hydroxy-3-propyl-4-[4-(1H-tetrazol-5-yl)butoxy]phenyl] ethanone, is an orally active antagonist of LTD4- and LTE4-induced responses in a variety of test systems. We prepared a new series of LT antagonists based on a proposed model of LY171883 binding to the LTE4 receptor in which the n-propyl and tetrazole moieties of LY171883 occupy those parts of the receptor to which the C1-C5 chain and the cysteinyl carboxyl of LTE4 bind, respectively. The new compounds have an acidic function corresponding to the glycine carboxyl of LTD4 linked through a heterocyclic group which is proposed to bind to the LTD4 receptor where the cysteinyl glycine amide bond of LTD4 binds. LY203647, 1-[2-hydroxy-3-propyl-4-[4-[2-[4-(1H-tetrazol-5-yl)butyl]-2H- tetrazol-5-yl]butoxy]phenyl] ethanone, showed good LTD4 antagonist activity with a suitable pharmacologic and toxicologic profile and has been chosen for clinical evaluation.

Antigen-induced edema formation, bronchoconstriction, and pulmonary vasospasm in the isolated perfused guinea pig lung. Evidence for a secondary edemagenic response

The effect of antigen (ovalbumin) challenge on pulmonary hemodynamics, bronchoconstriction, and fluid filtration was investigated in Ringer's-perfused (non-recirculating) lungs that had been passively sensitized in vitro. Bolus ovalbumin injection (30 micrograms) produced immediate increases in pulmonary arterial pressure, peak intratracheal pressure, and lung weight within 1 min and secondary marked increases in intratracheal pressure and lung weight from 120 to 200 min. Electron microscopy of antigen-challenged isolated lungs showed evidence of both septal and intraalveolar edema. Ionophore A23187 (100 micrograms) challenge of nonsensitized lungs produced immediate pulmonary responses similar to antigen, whereas secondary increases in lung weight were smaller. Arachidonic acid pretreatment (1 microM) potentiated immediate antigen-induced increases in intratracheal pressure but did not affect pulmonary responses to ionophore challenge. Putative mediators of anaphylaxis including histamine, leukotrienes B4, C4, D4, and E4, platelet-activating factor, and substance P produced immediate changes in pulmonary arterial and/or intratracheal pressure similar to antigen challenge. Only platelet-activating factor and substance P partially mimicked the secondary edema formation noted following antigen challenge. Thus, antigen challenge in in vitro sensitized guinea pig lungs produced both immediate and secondary responses characterized by increases in vascular pressure, airway pressure, and edema formation. This occurred in the absence of circulating blood-formed elements and without a massive influx of cells. Synergism between mediators such as histamine, the leukotrienes, platelet-activating factor, and substance P released following antigen challenge may be necessary to produce the complete pathophysiological sequelae associated with antigen challenge in the perfused guinea pig lung.

Leukotriene receptor antagonists. 4. Synthesis and leukotriene D4/E4 receptor antagonist activity of 4-(alkyl)acetophenone derivatives

Analogues of the leukotriene D4/E4 receptor antagonist LY171883 (1a) were synthesized in which the tetrazole was linked to the hydroxyacetophenone moiety by an all-methylene carbon chain. A key step in the synthesis involved a Wittig olefin-forming reaction between 3-methoxy-2-propylbenzaldehyde and the ylide derived from (4-carboxybutyl)triphenylphosphonium bromide to form the desired carbon chain. A regioselective Fries rearrangement was employed to form the o-hydroxyacetophenone. Compounds in which the tetrazole was separated from the acetophenone by four and five methylene groups were compared to the corresponding derivatives in which an oxygen atom linked the tetrazole chain to the aromatic ring for their ability to antagonize LTD4- or LTE4-induced contractions of the isolated guinea pig ileum. When compared to 1a, the "carba" analogue, 7a, showed nearly identical LTD4 antagonist activity. The LTE4 antagonist activity for these two compounds was also identical. In the shorter chain series, the "carba" analogue, 7b, showed enhanced LTD4 antagonist activity and approximately 10-fold greater LTE4 antagonist activity. These results suggest that the oxygen atom para to the acetyl group of 1a and 1b is not of major importance for association with the LTD4 or LTE4 receptor sites in the guinea pig ileum.

Structure-activity relationships (SAR) of the 3-alkyl substituents among a series of hydroxy-acetophenone leukotriene antagonists

LY171883 is an orally active antagonist of leukotriene (LT) D4 and LTE4. A series of related compounds varying the position and nature of the alkyl side chain were synthesized and evaluated for their ability to block LTD4-induced contraction of guinea pig ileum. Maximal activity was obtained with n-propyl, n-butyl, and n-pentyl substituents with slightly reduced activity for longer side chains. Polar groups on the side chain substantially reduced activity. Thus, it appears that the leukotriene receptor site requires a nonpolar alkyl group of moderate size at the 3-position on this type of receptor antagonist.

Leukotriene receptor antagonists. 2. The [[(tetrazol-5-ylaryl)oxy]methyl]acetophenone derivatives

A series of [[(tetrazol-5-ylaryl)oxy]methyl]acetophenones was synthesized and evaluated as antagonists of leukotriene D4 induced contractions of guinea pig ileum. Substitutions at the 3-position of the acetophenone with ethyl (66), propyl (68), butyl (83), and isobutyl (84) gave -log IC50 values of 7.9, 8.0, 7.8, and 7.7, respectively. Equally potent compounds were obtained when the tetrazol-5-yl group was connected to the second benzene ring in the para position with a chemical bond (67), methylene (68), or ethylene (71). For retention of high antagonist activity, the acetophenone should be substituted in the 2-position by a hydroxyl group and the tetrazole ring should have an acidic hydrogen atom. 1-[2-Hydroxy-3-propyl-4-[[4-(1H-tetrazol-5-ylmethy) phenoxy]methyl]phenyl]ethanone (68, LY1632443) has undergone extensive pharmacologic evaluation for its potential as an antiasthma agent.

Leukotriene receptor antagonists. 1. Synthesis and structure-activity relationships of alkoxyacetophenone derivatives

A series of derivatives of 2,4-dihydroxy-3-propylacetophenone(1) were prepared and examined for their ability to block leukotriene D4 (LTD4) induced contraction of guinea pig ileum. Straight-chain carboxylic acids where the carboxyl group was separated from the acetophenone moiety by varying numbers of methylenes were evaluated, and maximum activity was obtained with the pentamethylene acid (6). Examination of ring substitution showed that the 2-propyl-3-hydroxy-4-acetyl substitution pattern was required for maximum LTD4 antagonist activity. Additional chain terminal groups were examined, and the acidic 5-tetrazolyl group separated from the acetophenone moiety by four to seven methylenes (26, 23, 27, 28) gave excellent in vitro and in vivo activities. Compound 26 (LY171883) had the best balance of in vitro and in vivo activity. It lacked bronchospastic activity at the doses administered and has been chosen for clinical evaluation.

Pharmacologic analysis of LY188695 (KB-2413), 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)-benzimidazole difumarate, a potent histamine1 receptor antagonist

LY188695 was evaluated both in vitro and in vivo in the guinea pig to determine its pharmacologic profile. The compound antagonized histamine-induced contractions of ileum, aorta, and trachea with pKB values of 9.9, 9.9, and 9.2 respectively. In the lung parenchymal strip, LY188695 caused a rightward shift of the histamine concentration-response curve with a reduction in the maximal response at all antagonist concentrations tested. The reason for this effect is unknown, but it was not due to a nonspecific depressant action of the compound on the parenchyma. Selectivity was shown by its inactivity against leukotriene D4, bradykinin, prostaglandin F2 alpha, acetylcholine, norepinephrine, and serotonin on various guinea pig and rat smooth muscles. Similarly, H2 receptor-mediated relaxation of the rat uterus was unaltered by LY188695. Increases in total pulmonary impedance caused by i.v. histamine to anesthetized guinea pigs were reduced by as little as 3 micrograms/kg given orally 1 hour prior to histamine challenge. In this system, LY188695 was 15 times more potent than chlorpheniramine and 100 times more potent than terfenadine. Similar responses elicited by acetylcholine were not antagonized by LY188695. A duration of action greater than 4 hours was observed in this model. Ovalbumin given i.v. to sensitized guinea pigs increased total pulmonary impedance which was markedly decreased after oral administration of 30 or 100 micrograms/kg LY188695. These results indicate that LY188695 is a very potent antagonist of H1-mediated responses and suggest that this agent might be useful in disease states characterized by an overproduction of histamine.

Evaluation of LY163443, 1-[2-hydroxy-3-propyl-4-([4- (1H-tetrazol-5-ylmethyl)phenoxy]methyl) phenyl]ethanone, as a pharmacologic antagonist of leukotrienes D4 and E4

LY163443,1-[2-hydroxy-3-propyl-4-([4- (1H-tetrazol-5-ylmethyl)phenoxy]- phenoxy]methyl)phenyl]ethanone, antagonized LTD4-induced contractions of guinea pig ileum, trachea, and lung parenchyma. Tracheal contractions to LTE4 were also inhibited by LY163443. The compound had minimal effect against ileal responses to LTC4 and parenchymal contractions to LTB4. Furthermore, LY163443 had little to no effect against contractions of isolated smooth muscles to histamine, bradykinin, PGF2 alpha, carbachol, serotonin or U46619. LY163443, given by oral administration to guinea pigs, blocked LTD4-induced increases in total pulmonary impedance (TPI). Similar responses elicited by histamine or U46619 were unaffected. Increases in TPI in response to i.v. administration of LTC4 were antagonized by LY163443 given by the same route. Ovalbumin challenge also increased TPI in guinea pigs previously sensitized against this antigen. In such animals, pretreated with pyrilamine, propranolol, and indomethacin, oral administration of LY163443 blocked the increase in TPI caused by ovalbumin. Additionally, LTD4 given intradermally to guinea pigs caused a vascular leakage which was suppressed by prior oral administration of LY163443. Finally, LY163443 relaxed isolated guinea pig trachea previously contracted with LTD4, histamine, or carbachol. Relaxation of tissues contracted by these latter two agonists suggested some inherent airway smooth muscle relaxant properties of the molecule. This was further demonstrated by showing some bronchodilator activity in an in vivo setting. Thus, this pharmacologic profile indicates that LY163443, or a member of the same chemical family, warrants consideration as a possible therapeutic agent in the treatment of asthma and in diseases characterized by an overproduction of LTD4 and LTE4.

LY171883, 1-less than 2-hydroxy-3-propyl-4-less than 4-(1H-tetrazol-5-yl) butoxy greater than phenyl greater than ethanone, an orally active leukotriene D4 antagonist

LY171883, 1-less than2-hydroxy-3-propyl-4-less than 4-(h-tetrazol-5-yl)butoxy greater than phenyl greater than ethanone, proved to be a potent antagonist of leukotriene (LT) D4 in guinea-pig ileum, trachea and lung parenchyma. The compound had little or no effect on contractions of isolated tissues to LTB4, prostaglandin F2 alpha, serotonin, histamine, bradykinin or carbamycholine. Responses of trachea to U46619, a thromboxane A2 mimetic, were antagonized by LY171883, but the doses required were approximately 10-fold higher than those necessary to produce the same degree of antagonism against LTD4. U46619 produced weak ileal contractions that were not blocked by LY171883. LY171883 antagonized both LTD4- and antigen-induced increases in total pulmonary resistance in anesthetized guinea pigs. LTD4 given intradermally to guinea pigs caused vascular leakage which was suppressed by prior administration of LY171883. LTC4-induced contractions of isolated ilea were only minimally antagonized by LY171883 whereas this agent reduced LTC4-evoked increases in total pulmonary resistance. Trachea contracted by LTD4 were relaxed by LY171883. Likewise, trachea contracted by either histamine or carbamylcholine were relaxed by LY171883 suggesting that this compound has airway smooth muscle relaxing properties. In vivo experiments supported these observations. In concert with these findings, biochemical studies showed LY171883 to be a potent inhibitor of phosphodiesterase obtained from human polymorphonuclear leukocytes and various guinea-pig tissues. This pharmacologic analysis indicates that LY171883, or a congener, may be of therapeutic value in asthma and in disease states characterized by an overproduction of LTD4.

LY83583: an agent that lowers intracellular levels of cyclic guanosine 3',5'-monophosphate

A novel compound, LY83583 (6-anilino-5,8-quinolinedione), was found to lower basal levels of cyclic GMP (cGMP) in fragments of guinea-pig lung incubated in vitro. The lowering of cGMP was dose-related reaching a maximum of 72% at 5 X 10(-5) M. Basal levels of cyclic AMP (cAMP) were not lowered by LY83583. cGMP concentrations were also reduced in guinea-pig heart and cerebellum after incubation with LY83583. However, the drug did not alter the levels of this cyclic nucleotide in spleen. Exposure of lung fragments from sensitized guinea pigs to ovalbumin resulted in a marked increase in cGMP and cAMP. LY83583 prevented completely the accumulation of cGMP and attenuated the rise in cAMP. Similar results were obtained in rat cerebellum stimulated with kainic acid. The compound also blocked ovalbumin-induced release of slow reacting substance of anaphylaxis (leukotrienes) from guinea-pig lung. Subcutaneous administration of LY83583 to guinea pigs did not affect cGMP concentrations in vivo in lung, but the total amount of cGMP in spleen was reduced dramatically. This was accompanied by a marked splenomegaly. LY83585 did not inhibit lung guanylate cyclase. In fact, activity was increased in a cell-free preparation from guinea-pig lung. The mechanism by which LY83583 reduced concentrations of cGMP is presently unknown. Nevertheless, our studies suggest that LY83583 will be a valuable pharmacological tool to help elucidate the role of cGMP in biological events.

Production and antagonism of cutaneous vascular permeability in the guinea pig in response to histamine, leukotrienes and A23187

The method of Katayama et al. (Microbiol. Immunol. 22:89-101, 1978) for assessing cutaneous vascular permeability was modified and used to evaluate responses of the dermal vasculature to histamine, leukotriene (LT)C4, LTD4 and the ionophore A23187. These agonists were given intradermally, whereas antagonists and other types of inhibitors were administered i.v. Histamine was shown to cause vascular leakage via an H1 receptor. No evidence for H2 receptor activation or involvement of cyclooxygenase products was found. The results also suggested that a portion of the response to histamine was due to the liberation of LTD4. LTC4 produced a mixed response comprised of vasoconstriction and increased vascular permeability, the latter possibly due to its conversion to LTD4. FPL 55712 antagonized LTD4-induced permeability in a dose-dependent manner, whereas indomethacin had no effect. Neither pyrilamine nor FPL 55712 reduced the response to A23187. A dose of indomethacin that did not affect the response to A23187 when given alone markedly reduced the ability of ionophore to cause vascular leakage when combined with either pyrilamine or FPL 55712. Thus, histamine and LTD4, in combination with one or more of the cyclooxygenase products, may be involved in A23187-induced cutaneous vascular permeability. Finally, two calcium channel blocking agents, nifedipine and diltiazem, did not block the vascular leakage caused by A23187.

Pharmacologic analysis of two novel inhibitors of leukotriene (slow reacting substance) release

LY83583 , a quinolinedione , and LY151364 , a quinoxalinedione , were developed as inhibitors of leukotriene (slow reacting substance of anaphylaxis) release. They preferentially inhibited the release of leukotrienes over histamine from fragmented guinea-pig lung and rat peritoneal cells in vitro, regardless of whether the mediators were released immunologically by antigen or chemically by the divalent cationic ionophore, A23187. Similar results were obtained with rat peritoneal cells in vivo. In that system, comparison of LY83583 with disodium cromoglycate showed the former to preferentially inhibit release of leukotrienes, whereas the latter favored inhibition of histamine release. LY83583 did not significantly decrease antigen-induced bronchospasm in guinea pigs after i.v. administration of doses that approached toxic levels. In addition, LY83583 did not antagonize contractions to carbachol or histamine on guinea-pig trachea, prostaglandin F2 alpha-elicited contraction on guinea-pig ileum or contractions produced by serotonin on guinea-pig aorta. This agent, at 1 X 10(-5) M, reduced the maximal responses to bradykinin on ileum and caused a rightward displacement with a reduction in the maximal response to norepinephrine on guinea-pig aorta. In summary, LY83583 and LY151364 have interesting pharmacologic profiles which make them useful as tools in understanding the role of the leukotrienes in isolated tissue systems.

Evidence for multiple leukotriene D4 receptors in smooth muscle

Using pure leukotriene D4 (LTD4) as the agonist, we determined the dissociation constants, Kb and pA2 values, for the selective leukotriene antagonist FPL 55712 on guinea pig ileum, trachea, and parenchyma. Responses of the 3 tissues to LTD4 were competitively antagonized by FPL 55712. Kb and pA2 values were similar for trachea and parenchyma. However, these values differed from those obtained in ileum. We propose the existence of multiple LTD4 receptors, with those in lung differing from LTD4 receptors in ileum.

Slow reacting substance of anaphylaxis (SRS-A) release from guinea-pig lung parenchyma during antigen- or ionophore-induced contraction

A dual isolated organ technique comprised of a guinea-pig lung parenchymal strip and a guinea-pig ileum was used to determine if slow reacting substance of anaphylaxis (SRS-A) is released from parenchyma during contractions evoked by antigen (ovalbumin) or by ionophore (A23187). An immunologically sensitized parenchyma served as the primary target organ for ovalbumin and either a sensitized or unsensitized parenchyma was the target tissue for A23187; an unsensitized ileum functioned as the assay organ. In the presence of pyrilamine and indomethacin, ovalbumin or A23187 produced contractions of the parenchyma and concomitantly caused release of SRS-A from the lung strip which was indicated by a contraction of the ileum. The ileal response was antagonized by FPL 55712, whereas the parenchyma contractions were unaffected. Additional experiments were conducted in which parenchyma was contracted with histamine. At the height of the histamine contraction, the bathing fluid surrounding the parenchyma was removed and assayed on a pyrilamine-treated ileum. SRS-A was not detected, indicating that SRS-A release from parenchyma is not a function of tissue contraction per se, but is related to the antigen- and ionophore-induced contractions. To explain the lack of effect of FPL 55712 on parenchymal contractions to antigen or ionophore, we compared the degree of antagonism produced by FPL 55712 on SRS-A contraction of parenchyma and ileum. These experiments indicated the possibility that at least two different classes of SRS-A receptors exist and that those in the ileum and lung differ.

Schultz-Dale reaction in mouse trachea

A method was developed to induce contraction of immunologically sensitized mouse trachea by antigen (Schultz-Dale reaction). The response was mediated by immunoglobulin (Ig) E antibody directed against either the hapten DNP, the hapten carrier conjugate DNP-keyhole limpet hemocyanin (KLH), or the unmodified carrier KLH. Tracheal contractions were elicited by DNP-KLH, KLH, or DNP-bovine serum albumin (BSA) but not by DNP or BSA alone. This procedure represents a useful index of in vitro anaphylaxis in mouse airway smooth muscle.

Vasodilation and aging evaluated in the isolated perfused rat mesenteric vascular bed: preliminary observations on the vascular pharmacology of dobutamine

The influence of animal age of drug-induced vasodilation was investigated in the perfused rat mesentery constricted with norepinephrine. Responses to isoproterenol, a beta-receptor stimulant, decreased with increasing age. Also, there was a modest decline in the relaxation produced by papaverine. In contrast, dilation of the rat mesentery by acetylcholine, histamine, or nitroglycerin either did not change with age or the responses became somewhat larger. Dobutamine, a myocardial beta-receptor stimulant, produced a marked relaxation of the mesentery. A comparison of the action of isoproterenol and dobutamine revealed that isoproterenol stimulated vascular beta-receptors, whereas dobutamine relaxed the mesentery by antagonizing the tone produced by norepinephrine. The dilation resulting from the alpha-receptor-blocking action of dobutamine was unrelated to animal age.

Computerization of a bioassay: quantitation of slow reacting substance of anaphylaxis (SRS-A)

The bioassay for SRS-A using isolated guinea-pig ileum bathed in atropine and pyrilamine has been computerized resulting in a more accurate collection and calculation of data. Areas under the polygraph tracings are calculated by a computer interfaced with the recording polygraph. After comparison of ileal responses obtained with known amounts of SRS-A standard, the computer determined the relative amounts of SRS-A in unknown samples. The program provided for a correction to adjust for changes in tissue responsiveness. Using this bioassay, we showed that ovalbumin-induced release of SRS-A from sensitized guinea-pig lung was parallel to the release of histamine measured fluorometrically. Ethanol inhibited release of these mediators of anaphylaxis in a similar fashion. Conversely, isoproterenol reduced ovalbumin-induced release of SRS-A to a greater extent than the release of histamine. The versatility of this technique should enable other bioassays to be improved in addition to greatly facilitating the determination of various pharmacologic analyses.

On the measurement of vascular and respiratory smooth muscle responses in vitro

The action of drugs on circular smooth muscle from rabbit renal artery, renal vein, mesenteric vein, inferior vena cava, guinea pig bronchus, and mouse trachea was studied using an inexpensive modification of the method of Bevan, Nielsen and Owman, and Bevan and Osher. Two 30-gauge disposable stainless steel hypodermic needles supported the tissue rings in a standard 10-ml isolated muscle bath. All the blood vessels contracted to norepinephrine, histamine, and KCl. The veins, unlike the renal artery, did not respond maximally to KCl and did not contract at all to serotonin. The guinea pig bronchi contracted to carbachol, histamine, and KCl and relaxed to isoproterenol. The mouse trachea contracted maximally to carbachol, did not contract to histamine, and contracted to 50% of maximum in response to KCl. Thus, standard isolated tissue baths can be inexpensively adapted for the study of relatively small blood vessels and airways (about 1 mm in diameter).

Inhibition of antigen-induced mediator release from guinea pig lung by alcohols

Guinea pig bronchi sensitized to ovalbumin were set up in isolated tissue baths according to the method of Hooker and associates (1,2). In the presence of 10(-6)M atropine, pyrilamine, and indomethacin, concentrations of ovalbumin from 10(-9) to 10(-8) g per ml produced marked contraction of the bronchi. Generally, the antigen-induced contraction could be repeated every 45 to 60 min without tachyphylaxis. Ethanol (1.5 per cent), propanol (0.75 percent), butanol (0.25 per cent), and propylene glycol (1.5 per cent) decreased the contracile response to ovalbumin but either did not influence (ethanol and propylene glycol) or slightly reduced (propanol and butanol) responses of the bronchi to prostaglandin F2alpha. Trachea, bronchi, and parenchyma from sensitized guinea pigs were minced, washed, incubated in Krebs'-bicarbonate solution and challenged with 10(-6) and 10(-4) g per ml ovalbumin. Mediators released into the medium were assayed on unsensitized guinea pig ileum. All the alcohols suppressed mediator release. Circular dichroism demonstrated that the conformational integrity of ovalbumin was not altered by the concentrations of alcohols used in this study. These results show that antigen-induced mediator release is inhibited by alcohols and suggest caution when choosing a solvent for testing the effect of water insoluble anti-asthma compounds.