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

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

Role of immunoglobulins G1 and G2 in anaphylactic shock in the guinea pig

Heating serum from actively sensitised guinea pigs did not remove its ability to sensitise recipient animals in vivo and parenchymal lung strips in vitro to anaphylaxis. Thermoresistant antibodies should thus account for the transferable sensitising effect, which persists for at least 9 days. IgG1 and IgG2, contained in the serum, were separated by affinity chromatography to determine the importance and the participation of these subclasses in passive anaphylactic shock. IgG1, present in smaller amounts than IgG2, was more effective in sensitising isolated lung strips. The intravenous administration of ovalbumin to guinea pigs, which had been injected with 0.8 mg/kg of IgG1 or 2 mg/kg of IgG2 9 days beforehand, induced an intense bronchoconstriction with leucopenia and moderate thrombopenia, suggesting an as yet undescribed role for IgG2 in passive tissue sensitisation. The use of mepyramine, an antagonist of the histamine H1 receptor, WEB 2086, an antagonist of platelet-activating factor, and nordihydroguaiaretic acid, a dual inhibitor of cyclooxygenase and lipooxygenase, alone or associated, demonstrated that the anaphylactic contraction of lung strips from guinea pigs sensitised by IgG1 is mediated by histamine and arachidonate derivatives, whereas that of lung strips from guinea pigs sensitised with IgG2 is mostly mediated by histamine. In addition, the association of the three potential antagonists slightly reduced the anaphylactic contraction of lung strips provided by guinea pigs sensitised by serum. Our results, using a sensitisation procedure considered until now to involve exclusively IgE antibodies, indicate that IgG1 and IgG2 are in fact the essential antibodies for passive anaphylactic shock in the guinea pig.     

FPL 55712—An antagonist of slow reacting substance of anaphylaxis (SRS-A): A review

Compound FPL 55712 is a highly selective antagonist of SRS-A derived from guinea-pig, rat, man and dog. It equally antagonizes SRS (slow reacting substance) released by calcium ionophore from rat basophilic leukemia cells and peritoneal mono-nuclear cells and by compound 48/80 from cat paw. In comparatively high doses FPL 55712 significantly inhibits passive cutaneous anaphylaxis in rat and anaphylactic bronchoconstriction in guinea-pig and rat and acute anaphylactic shock in the monkey. It inhibits the antigen-induced rhythmic mechanical activity in chicken ileum and late phase of Schultz-Dale reaction in guinea-pig trachea and human bronchus. In addition, FPL 55712 inhibits the SRS-A-induced release of rabbit aorta contracting substance (RCS) from guinea-pig lung. FPL 55712 facilitates sputum clearance in allergic canine asthma. This compound also inhibits the guinea-pig ECF-A (eosinophil chemotactic factor of anaphylaxis)-induced eosinophil chemotactic response of guinea-pig eosinophils in vitro. Compound FPL 55712 is an invaluable pharmacological tool for the identification of SRS(A) and to help define the role of SRS-A in the pathophysiology of immediate hypersensitivity (e.g. anaphylaxis and allergic asthma). Clinical trials of FPL 55712 as an aerosol in allergic obstructive respiratory diseases in man and animals may help to further understand the mechanism(s) and chemical mediator(s) involved in these conditions.     

FPL 55712 — An antagonist of slow reacting substance of anaphylaxis (SRS-A): A review

Compound FPL 55712 is a highly selective antagonist of SRS-A derived from guinea-pig, rat, man and dog. It equally antagonizes SRS (slow reacting substance) released by calcium ionophore from rat basophilic leukemia cells and peritoneal mono-nuclear cells and by compound 48/80 from cat paw. In comparatively high doses FPL 55712 significantly inhibits passive cutaneous anaphylaxis in rat and anaphylactic bronchoconstriction in guinea-pig and rat and antigen-induced rhythmic mechanical activity in chicken ileum and late phase of Schultz-Dale reaction in guinea-pig trachea and human bronchus. In addition, FPL 55712 inhibits the SRS-A-induced release of rabbit aorta contracting substance (RCS) from guinea-pig lung. FPL 55712 facilitates sputum clearance in allergic canine asthma. This compound also inhibits the guinea-pig ECF-A (eosinophil chemotactic factor of anaphylaxis)-induced eosinophil chemotactic response of guinea-pig eosinophils in vitro. Compound FPL 55712 is an invaluable pharmacological tool for the identification of SRS(A) and to help define the role of SRS-A in the pathophysiology of immediate hypersensitivity (e.g. anaphylaxis and allergic asthma). Clinical trials of FPL 55712 as an aerosol in allergic obstructive respiratory diseases in man and animals may help to further understand the mechanism(s) and chemical mediator(s) involved in these conditions.     

SRSA-mediated bronchospasm by pharmacologic modification of lung anaphylaxis in vivo

Antigen challenge of actively sensitized guinea pigs results in the release of histamine, eicosanoids (products of the cyclooxygenase pathway of arachidonic acid metabolism) and slow reacting substance of anaphylaxis (SRS-A). By antagonizing the effects of histamine, serotonin, and acetylcholine, inhibiting the cyclooxygenase pathway and supplying arachidonic acid as substrate, the contribution of SRS-A to anaphylactic bronchospasm can be enhanced, thus allowing suitable quantitation of antagonists. This SRS-A mediated bronchospasm can be inhibited in a dose dependent fashion by FPL55712, a selective antagonist of SRS-A. This system represents an in vivo method capable of detecting compounds which inhibit SRS-A synthesis/release or SRS-A action at the effector organ.Presented in part at the Federation of American Societies for Experimental Biology meeting 1980, Anaheim, California.     

Heterogeneity of Drug Susceptibility of Mouse Active Anaphylactic Shock

To determine the main mediators for mouse anaphylactic shock, the suppression of active anaphylactic shock by cyproheptadine, an antagonist of histamine/serotonin, and CV-6209, an antagonist of platelet-activating factor (PAF), was systematically evaluated using various mouse strains. The suppression was quite heterogeneic depending on the mouse strain and method for sensitization. When sensitization was done with bovine serum albumin (BSA) plus Bordetella pertussis organisms, anaphylactic shock in C57BL/6N mice was suppressed by cyproheptadine but not by CV-6209. In contrast, shock in C3H/HeN and WBB6F1-W/W^V mice was suppressed by CV-6209 but not by cyproheptadine. Shock in BALB/c mice was suppressed by both agents but that in WBB6F1-+/+ mice was not at all by either one. DS and BDF1 mice showed differences due to the length of the sensitization period; shock was not suppressed by cyproheptadine with a shorter sensitization (9 to 11 days) but clearly suppressed with prolonged sensitization of 14 to 15 days. Shock in DS, WBB6F1-+/+ and BDF1 mice, which was not suppressed by either agent alone, was strongly suppressed by the combination of the two agents. In animals which had been sensitized with BSA emulsified with Freund's complete adjuvant (FCA) and given DL-propranolol as a shock potentiator, a similar pattern of drug susceptibility as that in the pertussis-vaccinated animals was obtained in general, although a discrepancy was seen with regard to the suppression of CV-6209 in C3H/HeN and BDF1 mice. Synergistic suppression by CV-6209 and cyproheptadine was also very clear with the WBB6F1-+/+ mice sensitized using FCA. In addition, results quite similar to those with cyproheptadine were obtained with the other two antihistamines, triprolidine almost devoid of antiserotonin activity and oxatomide, in testing with BDF1 mice sensitized using Bordetella pertussis organisms. From these findings, the conclusion is that histamine and PAF play major roles solely or in combination in mouse active anaphylactic shock.     

Effect of inhibition of arachidonic acid metabolism on anaphylaxis of guinea pig lung strips

The effect of inhibitors of the cyclooxygenase and/or lipoxygenase pathways of arachidonic acid metabolism on the anaphylactic contraction of lung parenchymal strips from ovalbumin sensitized guinea pigs was studied. Indomethacin, a selective cyclooxygenase inhibitor, significantly enhanced the anaphylactic contraction at 10^–6 M with no effect at 10^–5 or 10^–4 M. By contrast, nordihydroguaiaretic acid (NDGA, 10^–5 and 10^–4 M), a lipoxygenase inhibitor, and 1-phenyl-3-pyrazolidinone (phenidone, 10^–4 M), an inhibitor of both the cyclooxygenase and lipoxygenase markedly inhibited the anaphylactic contractile response. The pattern of inhibition was similar to that produced by FPL 55712, an antagonist of slow reacting substance of anaphylaxis (SRS-A), and was characterized by a decrease in the maximum tension and in the duration of the contraction. The results suggest that inhibition of the lipoxygenase pathway reduced anaphylactic contraction of guinea pig lung strips possibly by inhibiting the synthesis and release of SRS-A.     

Heterogeneity of Drug Susceptibility of Mouse Active Anaphylactic Shock

To determine the main mediators for mouse anaphylactic shock, the suppression of active anaphylactic shock by cyproheptadine, an antagonist of histamine/serotonin, and CV-6209, an antagonist of platelet-activating factor (PAF), was systematically evaluated using various mouse strains. The suppression was quite heterogeneic depending on the mouse strain and method for sensitization. When sensitization was done with bovine serum albumin (BSA) plus Bordetella pertussis organisms, anaphylactic shock in C57BL/6N mice was suppressed by cyproheptadine but not by CV-6209. In contrast, shock in C3H/HeN and WBB6F1-W/W^V mice was suppressed by CV-6209 but not by cyproheptadine. Shock in BALB/c mice was suppressed by both agents but that in WBB6F1-+/+ mice was not at all by either one. DS and BDF1 mice showed differences due to the length of the sensitization period; shock was not suppressed by cyproheptadine with a shorter sensitization (9 to 11 days) but clearly suppressed with prolonged sensitization of 14 to 15 days. Shock in DS, WBB6F1-+/+ and BDF1 mice, which was not suppressed by either agent alone, was strongly suppressed by the combination of the two agents. In animals which had been sensitized with BSA emulsified with Freund's complete adjuvant (FCA) and given DL-propranolol as a shock potentiator, a similar pattern of drug susceptibility as that in the pertussis-vaccinated animals was obtained in general, although a discrepancy was seen with regard to the suppression of CV-6209 in C3H/HeN and BDF1 mice. Synergistic suppression by CV-6209 and cyproheptadine was also very clear with the WBB6F1-+/+ mice sensitized using FCA. In addition, results quite similar to those with cyproheptadine were obtained with the other two antihistamines, triprolidine almost devoid of antiserotonin activity and oxatomide, in testing with BDF1 mice sensitized using Bordetella pertussis organisms. From these findings, the conclusion is that histamine and PAF play major roles solely or in combination in mouse active anaphylactic shock.     

Spasmogenic properties of platelet-activating factor: evidence for a direct mechanism in the contractile response of pulmonary tissues.

Platelet-activating factor (1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine; PAF) induces a specific, dose-dependent contraction of guinea pig lung parenchymal strips with an ED50 value of 10(-9) M. The smooth muscle contractile activity of PAF in this system was not effected by the H1-blocking antihistamine, pyrilamine (10(-6) M), the prostaglandin synthesis inhibitors, indomethacin (10(-5) M), aspirin (10(-4) M), or sulfinpyrazone (5 X 10(-4) M), the leukotriene synthesis inhibitor, nordihydroguaiaretic acid (NDGA; 10(-5) M), the leukotriene antagonist FPL 55712 (10(-6) M) or the inhibitor of arachidonic acid metabolism, eicosatetraynoic acid (ETYA; 2 X 10(-5) M). The role of platelets in this system was also investigated. PAF-mediated contractions were not attenuated following platelet depletion using nitrogen mustard, nor were they augmented by the addition of exogenous platelets. Furthermore, isolated platelets incubated with PAF did not release stable substances spasmogenic for lung parenchymal strips. Finally, contractile activity of PAF was demonstrated in lung parenchymal strips from rats, a species whose platelets are insensitive to PAF at elevated concentrations. Taken together, these data show that PAF contracts smooth muscle of guinea pig lung parenchyma independently of endogenous histamine, arachidonic acid metabolites, or platelets trapped within the pulmonary vasculature. It is concluded, therefore, that PAF may act directly on contractile cells of the lung.     

Histamine in the tissues of the marsupial Setonix brachyurus (the quokka).

Passive cutaneous anaphylactic (PCA) reactions in the marsupial Setonix brachyurus (the quokka) were completely inhibited by the histamine antagonist mepyramine maleate, but were unaffected by disodium cromoglycate or the serotonin antagonist, methysergide. Histological examination of quokka skin indicated that mast cell degranulation occurred during the PCA reaction in this marsupial and animals whose skin was relatively deficient in mast cells were poor PCA recipients. In contrast to many eutherian (placental) species, this marsupial was found to lack histamine in blood leukocytes and platelets. Also, while the peritoneal mast cells of rats and mice contain large quantities of histamine, this amine was not detected to quokka peritoneal washings, even after the induction of a peritoneal exudate or the regular intraperitoneal injection of antigen. Immunologic challenge of quokka blood or peritoneal cells did not induce the synthesis of histamine, but histamine release was elicited from sensitized quokka lung by antigenic challenge.     

Effects of histamine H1-receptor blockade on respiratory and cardiac manifestation of systemic anaphylaxis

Summary In vivo anaphylaxis is associated with respiratory distress and cardiovascular failure. The present investigation was designed to further characterize respiratory and cardiac anaphylactic events. In guinea pigs, sensitization was produced by subcutaneous application of ovalbumin together with Freund's adjuvant. Fourteen days after sensitization, the effects of an intravenous infusion of ovalbumin were tested in the anesthetized artificially ventilated guinea pigs. The renewed application of the antigen induced an initial increase of left ventricular pressure which was followed by a rapid decrease 5 min after antigenic challenge. Enddiastolic left ventricular pressure increased within 3 min, thus indicating left ventricular pump failure. In the same time range, ECG recordings uniformly showed signs of acute myocardial ischemia. In addition, heart rate steadily decreased. All animals died within 15 min. Simultaneously with cardiac anaphylactic malfunction, severe arterial hypoxia and carbon dioxide retention occurred, revealing respiratory distress.Histamine is known as a potent bronchoconstrictor via histamine H₁-receptor stimulation. Administration of H₁-recpetor antagonists to improve respiration may therefore provide further information on the contribution of pulmonary malfunction to anaphylactic cardiovascular shock. Therefore, additional experiments were performed with sensitized guinea pigs pretreated with the histamine H₁-receptor blocker mepyramine. In these experiments the antigenic challenge induced a dissociation of cardiac and respiratory manifestation of anphylaxis. Despite inhibition of hypoxia and carbon dioxide retention, left ventricular pump failure and occurrence of myocardial ischemia were delayed but not suppressed.It is concluded that histamine is an important mediator of anaphylactic respiratory distress. However, vasoactive anaphylactic mediators other than histamine are primarily involved in anaphylactic cardiac malfunction occurring during the later phase of systemic anaphylaxis.Supported by grant Fe 250/1-1 from the Deutsche Forschungsgemeinschaft (DFG).     

A new method of testing anti-allergic drugs

Rats were sensitized with a single intraperitoneal dose of bovine serum albumin in alhydrogel plus Bordetella pertussis vaccine, and local anaphylaxis was elicited in the paw by soluble antigen 2 weeks later. The response was mainly due to IgE-type antibodies and proved to be highly sensitive to beta-adrenoceptor agonists. Dexamethasone inhibited the response after a lag phase. Methysergide, disodium chromoglycate, diethylcarbamazine, BW 775/c, nordihydroguarjaretic acid, and FPL 55712 were also suppressive, while mepyramine was without effect. A synergism between methysergide and FPL 55712 was shown. Active local paw anaphylaxis appears to be adequate and easily applicable for large-scale screening of anti-allergic drugs.     

Leucotrienes,SRS-A and the vascular manifestations of PCA

In order to study possible mediators of the vascular manifestations of passive cutaneous anaphylaxis (PCA), several arachidonic acid metabolites were injected into guinea-pig skin. SRS-A, LTB4, LTC and LTD increased vascular permeability, responses to LTs being enhanced by PGE2. Mepyramine inhibited responses to histamine, but not those to SRS-A and LTs: the latter were inhibited by the SRS-A antagonist FPL-55712. Both mepyramine and FPL-55712 exert limited inhibitory effects on vascular permeability during PCA. Leukotrienes may contribute towards vascular permeability during PCA.     

Passive air-pouch anaphylaxis in rats. II. Pharmacological characterization

The effects of some antiallergic agents on passive air-pouch anaphylaxis (PAPA) in the dorsal skin of rats were investigated by measuring plasma exudation and histamine content in the pouch fluid. Antiallergic agents, disodium cromoglycate (DSCG), tranilast and ketotifen, dose dependently inhibited both plasma exudation and histamine release, except that ketotifen showed a dose-unrelated inhibition of histamine release. An antihistamine, pyrilamine, suppressed plasma exudation without affecting histamine release. A cyclooxygenase inhibitor, indomethacin, and a 5-lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), showed no significant effect. A slow-reacting substance of anaphylaxis antagonist, FPL55712, exerted no effect at 0.3 and 3.0 micrograms/ml, but at 50 micrograms/ml it suppressed not only plasma exudation but also histamine release. Dexamethasone suppressed plasma exudation dose dependently without inhibiting histamine release significantly. A beta-stimulant, isoproterenol, and prostaglandin E2 also exerted significant inhibitory effects on plasma exudation but not on histamine release at 1 mg/ml. Theophylline inhibited both plasma exudation and histamine release. These observations indicate that PAPA is useful for studying antiallergic agents.     

Studies on vascular permeability increasing factors involved in 48-hour homologous PCA in the mouse ear

Several attempts were made to elucidate the possible role of histamine, serotonin, leukotrienes C4 (LTC4) and D4 (LTD4), and prostaglandin E1 (PGE1) as vascular permeability increasing factors involved in 48-hour homologous passive cutaneous anaphylaxis (PCA) in the mouse ear. Increased vascular permeability in the mouse ear caused by the mediator injection or PCA was assessed quantitatively by measuring the amount of extravasated dye. In skin reactions, all of the mediators used in the present study significantly increased vascular permeability. The most potent mediator was serotonin, which increased the vascular permeability from a concentration of 10(-8) g/ml, and the activity was about 100 times higher than that of histamine on a weight basis. Vascular permeability increasing activity of LTC4 was about 10 times higher than that of histamine, and LTD4 and PGE1 were also more potent than histamine. Increases of vascular permeability caused by histamine, serotonin, LTC4 and LTD4 were significantly potentiated by injecting 10(-6) g/ml of PGE1 simultaneously. Histamine-, serotonin- and LTC4-induced skin reactions in the mouse ear were suppressed significantly by the administrations of chlorpheniramine, methysergide and FPL 55712, respectively. In contrast, though chlorpheniramine and methysergide suppressed also mouse ear PCA (about 50 and 40%, respectively), neither FPL 55712, indomethacin nor BW 755C suppressed it. These results strongly suggest that the most important mediator involved in mouse ear PCA is histamine and that serotonin also plays an important role in the increase of vascular permeability caused by PCA. Despite their potent vascular permeability increasing activity LTC4, LTD4 and PGE1 do not seem to play an important role in mouse ear PCA.     

Mechanisms of leukotriene-induced contractions of guinea pig airways: leukotriene C4 has a potent direct action whereas leukotriene B4 acts indirectly

The leukotrienes (LT's) are a group of arachidonic acid derivatives implicated as mediators of allergic bronchoconstriction and acute inflammation. Tracheal spirals and strips of lung parenchyma from guinea pigs were used under non-flow conditions to characterize the contractions caused by LTA4, LTB4 and LTC4. Cumulative administrations of leukotrienes desensitized the lung strip, whereas non-cumulative dose-response relationships for the leukotrienes and histamine were reasonably parallel. Half maximal contractions of the lung strips were obtained at a final bath concentration of 1 nM for LTC4 and 300 nM for LTA4 or LTB4, as compared with 6 000 nM for histamine. In the trachea, LTC4 was approximately 100 times more potent than LTA4 and histamine. Leukotrienes B4 and C4, but not acetylcholine or histamine, elicited release of the bronchoconstrictive thromboxane A2 from the lung under non-flow conditions. Indomethacin blocked the contractile response to LTB4, whereas the contractile effect of LTC4 remained unaltered. The beta-adrenoceptor agonist isoproterenol and the LTC4 antagonist FPL 55712 attenuated the contraction, but not the release of thromboxane A2, induced by LTC4. Changing to a perifusion technique rendered the lung strips less sensitive to the direct action of LTC4, and released thromboxane A2 now contributed significantly to the contractile response. In addition, the perifusion experiments indicated that LTB4 released histamine as well. We conclude that the chemoattractant LTB4 is an indirectly acting bronchoconstrictor, whereas the slow reacting substance LTC4 contracts the airway muscle by a predominantly direct mechanism. The exquisite bronchoconstrictive activity of LTC4 may be unrelated to its ability to induce formation of thromboxane A2.     

Pharmacologic properties of FPL 55712 administered by aerosol

FPL 55712 was investigated by the aerosol route of administration for efficacy at protecting against leukotriene-induced bronchoconstrictions in guinea pigs and for mediator release inhibitory activity in passively sensitized rats. In the studies to investigate leukotriene antagonism; anesthetized, spontaneously breathing guinea pigs were pretreated with propranolol and were exposed via tracheal cannula to aerosols generated by a Monaghan nebulizer. Subsequently, the animals were artificially ventilated and challenged with LTD₄ or LTE₄ (25 g/kg, i.v.). FPL 55712 produced a concentration-dependent inhibition of LTD₄ and LTE₄-induced bronchoconstriction (IC₅₀'s 0.5% and 0.8%, respectively). Although the biologic half-life of FPL 55712, administered intravenously, was very short (1.7 minutes against LTD₄ and 1.2 minutes against LTE₄) after aerosol administration the biological half-life was surprisingly long (120 minutes against LTD₄ and 90 minutes against LTE₄). Aerosolized FPL 55712 also possessed weak antiallergic activity in comparison to disodium cromoglycate when measured as an inhibitor of IgE-mediated anaphylactic bronchoconstriction in rats (IC₅₀'s of 2.0% and 0.01%, respectively). Thus, these studies demonstrate that, when administered by aerosol, FPL 55712 is effective at protecting against leukotriene-induced bronchoconstrictions, exhibits a long duration of action and also possesses weak antiallergic activity.     

Effect of non-steroidal anti-inflammatory drugs (NSAID) on the histamine release induced by compound 48/80 and cardiac anaphylaxis in guinea-pig isolated heart

Histamine release from guinea pig heart treated with compound 48/80 was potentiated by the cyclooxygenase inhibitors indomethacin and piroxicam but not by aspirin or phenylbutazone. This differential effect suggests that the potentiation is not merely due to an inhibition of prostaglandin synthesis. Piroxicam potentiated the histamine release induced by cardiac anaphylaxis whereas indomethacin reduced this effect. The SRS-A antagonist FPL 55712 inhibited histamine release induced by cardiac anaphylaxis, but not that evoked by compound 48/80, and also prevented the potentiation due to indomethacin and piroxicam. In total, these data suggest that the potentiation of histamine release by piroxicam and indomethacin is probably due to a diversion of arachidonic acid metabolism from the cyclooxygenase to the lipoxygenase pathways. The resulting lipoxygenase products may then regulate histamine release, with the secretion due to antigen being more sensitive to such modulation than that evoked by compound 48/80.     

The effect of ablation of eosinophils on immediate-type hypersensitivity reactions.

The effect of ablation of eosinophils on hypersensitivity reactions in guinea-pigs was tested by administration of rabbit antiserum to the eosinophil (AES) and by administration of glucocorticoids. Both AES and methylprednisolone ablated eosinophils from the blood and peritoneal cavity of test animals. Neither administration of AES nor methylprednisolone, however, altered passive cutaneous or systemic anaphylactic reactions when compared to reactions occurring in control animals treated with normal rabbit serum (NRS). Also there was no consistent effect of AES on the intensity of the Arthus reaction. The effect of ablation of eosinophils on histamine release in the passively sensitized peritoneal cavity of the guinea-pig was also tested. In five experiments a significant reduction in histamine release was seen in AES-treated animals. Ablation of eosinophils by cortisone acetate also resulted in a marked reduction in the quantity of histamine released into the peritoneal cavity following passive sensitization and antigen challenge. Histamine release following intraperitoneal injection of compound 48/80 was not affected by either the prior administration of AES or cortisone acetate, suggesting that the stores of histamine were not depleted by these agents. Overall these results suggest that eosinophils do not play a prominent role in initial expression of immediate-type hypersensitivity reactions where the density of these cells in tissues is low. When present in larger numbers, however, eosinophils may contribute to histamine release in immediate-type reactions.     

Effect of cinnarizine on IgE antibody-mediated experimental allergic reactions in guinea pigs

The anti-allergic activity and mechanism of cinnarizine was investigated in guinea pigs. Nifedipine, a calcium antagonist, and tranilast, a potent, orally active anti-allergic agent, were used as comparative drugs. Cinnarizine protected against fatal systemic anaphylactic shock in guinea pigs passively sensitized with IgE antibody. Cinnarizine reduced many of the features of severe respiratory disorders. Nifedipine and tranilast showed similar effects. Cinnarizine and nifedipine inhibited the contractile response to antigen of sensitized tracheal smooth muscle when the challenge was carried out at low antigen concentrations. Tranilast showed a tendency to inhibit the antigen-induced contraction of tracheal smooth muscle. Cinnarizine and nifedipine inhibited Ca-induced contraction in potassium-depolarized tracheal smooth muscle, tranilast had no effect. Cinnarizine showed antagonistic action to the contraction by histamine or leukotriene D4 (LTD4) of tracheal muscle. Nifedipine showed similar antagonistic action, although its potency is lower than cinnarizine. Tranilast showed slight antagonistic action to LTD4. Antigen-induced release of histamine and slow reacting substance of anaphylaxis (SRS-A) from sensitized lung tissues was inhibited by nifedipine and tranilast but not by cinnarizine. The release of histamine and SRS-A from lung tissues by calcium ionophore A23187 was inhibited by nifedipine and tranilast but not by cinnarizine. These results suggest that the anti-allergic action of cinnarizine is mainly due to the antagonistic action to allergic mediators and not by interfering with the release of mediators. Cinnarizine's mechanism seems to be related to its antagonistic action to Ca in smooth muscle, but not to the transport of Ca in releasing the anaphylactic chemical mediators in mast cells and other target cells.