Histamine as an autocrine growth factor in experimental mammary carcinomas

The antisecretory effect of DS-4574, a mast cell stabilizer with peptidoleukotriene antagonism, on the hypersecretion of gastric acid stimulated by several secretagogues was examined in the pig. Goettingen miniature pigs with chronic gastric fistula were used. Intramuscular injection of carbachol (60 g/kg), tetragastrin (50 g/kg) or histamine (200 g/kg)-induced gastric acid hypersecretion. Intraduodenal administration of DS-4574 (10 and 20 mg/kg) significantly inhibited both the hypersecretion induced by carbachol and that by tetragastrin. On the other hand, DS-4574 (50 mg/kg, intraduodenal) did not suppress histamine-induced hypersecretion. In thein vitro study, no effect on hog gastric K⁺-dependent ATPase activity was found at concentrations of DS-4574 from 10^–7 to 10^–4 M. These results were highly similar to those in the rat. The suppression of histamine release from histamine-containing cells in the gastric mucosa of the rat was concluded to be an antisecretory effect of DS-4574.     

Antiallergic activity of 6-(2-cyclohexylethyl)-[1,3,4]thiadiazolo- [3,2-a]-1,2,3-triazolo-[4,5-d]pyrimidin-9(3H)-one (DS-4574) in rats.

The antiallergic activity of DS-4574 was evaluated in several commonly used rat models for allergic diseases. In passive cutaneous anaphylaxis, DS-4574 given intravenously and orally induced dose-dependent inhibition with ID50 values of 0.55 and 2.8 mg/kg, respectively. In contrast, this compound had no antagonistic activity against the histamine- and serotonin-induced cutaneous vascular permeability. In lung anaphylaxis, DS-4574 inhibited pulmonary function changes induced by the antigen in a dose-dependent manner when it was given intravenously and orally, the ID50 values being 0.04 and 0.89 mg/kg, respectively. DS-4574 also inhibited antigen-induced histamine and leukotriene release in passive peritoneal anaphylaxis following oral administration. In addition, this compound prevented antigen-induced histamine release in passively sensitized mast cells in vitro. These potent activities of DS-4574 in in vivo and in vitro models of immediate-type hypersensitivity reactions suggest that this compound could be useful in the treatment of allergic diseases including asthma.     

Effects of infused histamine on asthmatic and normal subjects: comparison of skin test responses

The effect of histamine infused intravenously at sequentially increasing concentrations (0.05, 0.1, 0.25, 0.5, and 1 μ/kg/min) on the wheat responses to intradermal histamine and compound 48/80 in eight normal and five asthmatic subjects and to allergen skin tests in five asthmatic subjects was measured. These measurements were repeated following pretreatment with the H-1 antagonist hydroxyzine or the H-2 antagonist cimetidine, either alone or in combination. Histamine infused in progressively increasing concentrations had no effect on histamine, compound 48/80, or allergen skin tests either before or after H-1 or H-2 antihistamine treatment. No significant differene was found in the concentration of histamine or compound 48/80 required to elicit a 10-mm wheat in normal or asthmatic patients. Pretreatment with the H-2 antagonist alone had no effect on histamine or compound 48/80 skin tests in either group. However, the H-1 antagonist significantly reduced the wheat response to histamine (p < 0.05 normal; p < 0.025 asthmatics) and compound 48/80 (p < 0.05 normal; p < 0.025 asthmatics) in both groups. The combination of H-1 and H-2 histamine antagonists was not significantly different from the H-1 antagonist alone. Antigen skin testing was suppressed 82% by the hydroxyzine alone; no significant suppression was induced by cimetidine alone, and the combination of hydroxyzine plus cimetidine was only slightly more effective than hydroxyzine alone. The results indicate that blockade of histamine H-2 receptors with cimetidine has little or no additive effect on H-1 antagonist-suppressed skin test responses to histamine, compound , or antigen. Furthermore, the capacity of histamine to suppress histamine release in vitro from basophils was not demonstrated in vivo assessing skin mast cell responses. This observation combined with earlier studies on the human lung mast cell, which also failed to demonstrate that histamine had an inhibitory action, suggests that the human mast cell may not respond to histamine like the basophil and that this discrepancy may represent a fundamental difference in the cell types.     

Inhibitory effect of traxanox sodium on IgE-mediated histamine release from passively-sensitized mast cells of the rat in vitro

Traxanox sodium, a benzopyranopyridine derivative showing a potent oral antiallergic activity in the rat, was compared with disodium cromoglycate (DSCG) for ability to block the release of histamine from the rat mast cell in vitro. Traxanox sodium showed dose-, antigen- and time-dependent inhibiton of the IgE-mediated release of histamine. The 50% inhibitory concentration was 0.04 microM for traxanox sodium, 1 microM for DSCG and 660 microM for theophylline. All these drugs blocked the release of histamine potentiated by preincubation of the mast cell with 10 micro M adenosine at lower concentrations than those which could inhibit the IgE-mediated histamine release. In addition, traxanox sodium at concentration of 1-100 microM inhibited the histamine release caused by 0.25 microgram/ml compound 48/80 in the presence and absence of calcium, and the drug at 100 micro M slightly inhibited the release caused by 0.2 microgram/ml ionophore A23187. These results suggest that traxanox sodium is a more potent inhibitor than DSCG on the histamine release from the mast cells of the rat, and a part of its antiallergic action is due to a selective inhibition of the immunological release of allergic mediators from the mast cell.     

Inhibition of passive cutaneous anaphylaxis (PCA) by azelastine: dissociation of its antiallergic activities from antihistaminic and antiserotonin properties

Azelastine and methysergide injected i.v. 5 min prior to antigen challenge and disodium cromoglycate (DSCG) injected i.v. immediately before antigen challenge produced dose-dependent inhibition of IgE-mediated 72 h passive cutaneous anaphylaxis (PCA) responses with ID50S of 0.3, 0.2 and 1.0 mg/kg, respectively. Thus, azelastine is about three times as effective as DSCG (a mast cell stabilizing agent) and somewhat less active than methysergide (a specific serotonin "D" receptor antagonist). Oral administration of azelastine and other drugs 2 h prior to antigen challenge produced strong inhibitory effects on PCA. The ID50S (mg/kg) were as follows: azelastine = 1.4; astemizole = 1.6; ketotifen = 2.0; aminophylline = 4.6; and diphenhydramine = 10.9. After 4 h of oral administration, azelastine and other drugs inhibited PCA responses with the following ID50S (mg/kg): azelastine = 1.8; astemizole = 2.3; ketotifen = 2.3; and aminophylline = 12.5. Azelastine administered orally 24 h before antigen challenge was still capable of exerting significant anti-PCA activity with an ID50 of 2.6 mg/kg, whereas none of the other drugs tested produced any significant inhibitory effects on PCA. In subsequent experiments, it was established that the antiallergic and antihistaminic activities of azelastine are inseparable 2 h after oral administration (ID50 of azelastine mg/kg, p.o., 2 h: PCA = 2.6 and histamine = 3.1). However, the persistence of the oral antiallergic (anti-PCA) effects of azelastine for 24 h (ID50 = 3.7 mg/kg) does not seem to be associated with its antihistaminic or antiserotonin activities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of C5a-induced basophil degranulation by disodium cromoglycate

Injection of purified porcine C5a into 24-hr basophil-rich cutaneous basophil hypersensitivity sites in the dose range 10^–12–10^–10 moles/site produced cutaneous basophil anaphylaxis (CBA). The H₁ anti-histamine antagonist mepyramine, given orally (3.0–30 mg/kg), inhibited the vasopermeability, but not the basophil degranulation, characteristic of CBA. The antiallergy agent disodium cromoglycate (DSCG), administered intravenously (3.0–30 mg/kg), inhibited vasopermeability and basophil degranulation. DSCG inhibition of mast cell degranulation was not important in the inhibition of CBA, since intact mast cells were found to be depleted at basophil-rich sites and absent at C5a-induced CBA sites from animals treated with DSCG.C5a at 10^–11 moles/site also induced vasopermeability and mast cell degranulation in normal guinea pig skin. Vasopermeability, but not mast cell degranulation, was inhibited by mepyramine at 30 mg/kg p.o. However, DSCG at 10 mg/kg i.v. failed to inhibit either the vasopermeability or the mast cell degranulation of this reaction. These results indicate that C5a induces the degranulation of both basophils and mast cells in the guinea pig, and that C5a-induced degranulation of basophils, but not mast cells, is inhibited by DSCG.     

Effect of chinese herbal medicines and disodium cromoglycate on IgE-dependent histamine release from mouse cultured mast cells

We examined the effect of anti-allergic Chinese herbal medicines such as Ma-Xing-Gan-Shi-Tang (MXGST) and Xiao-Feng-San (XFS), and a mast cell stabilizer, disodium cromoglycate (DSCG) on histamine release from mouse cultured mast cells. The mast cells (ILMCMC) were obtained by culturing mouse bone marrow cells for 3–6 weeks in the presence of IL-3. Some of the cells (FMCMC) were further cultured with a fibroblast cell line, 3T3 for 3 weeks. FMCMC had safranin-positive granules and released histamine in response to compound 48/80, whereas ILMCMC failed to do so. MXGST and XFS at 4–40 μg/ml inhibited IgE-dependent histamine release from ILMCMC but not from FMCMC. On the contrary, DSCG at 10−4 M inhibited histamine release from FMCMC but not from ILMCMC. Chinese herbal medicines and DSCG may act on different types of mast cells.     

Inhibition of rat peritoneal mast cell exocytosis by frusemide: A study with different secretagogues

It has been reported that the loop diuretic frusemide can prevent exercise induced asthma, and that this effect may be due to the inhibition of mast cells in the airway. By using various mast cell secretagogues which increase intracellular calcium via different routes, this study attempted to elucidate the mechanism of the mast cell stabilizing action of frusemide. As well as confirming that immunologically induced histamine release from rat peritoneal mast cells was dose dependently inhibited by frusemide (10⁻³–10⁻⁵ M), the present study has extended the observation to histamine release induced by compound 48/80. The inhibitory potency was however less in the case of compound 48/80 induced release. Frusemide induced inhibition by the two secretagogues was decreased by drug preincubation. In contrast, histamine release induced by ionophore A23187 and thapsigargin was not inhibited by frusemide. The prototype antiallergic compound disodium cromoglycate (DSCG) demonstrated a similar specificity pattern against the various secretagogues. Another loop diuretic, bumetanide, did not show the same results as frusemide on rat peritoneal mast cell degranulation. Hence it is concluded that frusemide does not inhibit immunological activation of mast cells via its diuretic Na⁺/K⁺/Cl⁻ co-transporter capacity. Instead, it protects mast cells in a similar manner to DSCG. accepted by W. Lorenz     

Actions and cross-reactivity of antiallergic agents and a calcium channel antagonist on rat peritoneal mast cells. Difference in the action mechanisms and cross-reactivity among the agents

The actions of the antiallergic agents, disodium chromoglycate (DSCG), tranilast and ketotifen, and of a calcium channel antagonist, nicardipine, and cross-reactivity among the agents were examined by observing the inhibition of⁴⁵Ca uptake and histamine release in rat mast cells stimulated by antigen and compound 48/80 (comp. 48/80).

1. All agents inhibited⁴⁵Ca uptake and histamine release in mast cells stimulated by antigen. The inhibition of⁴⁵Ca uptake by the antiallergic agents paralleled the inhibition of histamine release, while nicardipine inhibition of⁴⁵Ca uptake was stronger than its inhibition of histamine release.
2. The action of DSCG on⁴⁵Ca uptake and histamine release was significantly decreased in cells stimulated with antigen and phosphatidylserine (PS), while tranilast inhibition of histamine release was not affected by the addition of PS despite a significant decrease in the inhibition of⁴⁵Ca uptake.
3. The inhibitory effect of DSCG and tranilast was significantly lower in mast cells stimulated by comp. 48/80 than in the cells stimulated by antigen.
4. Tachyphylaxis was observed in cells re-exposed to DSCG and tranilast following previous exposure to the agents.
5. Cross-reactivity was found between DSCG and tranilast.

     

The characterization of lodoxamide,a very active inhibitor of mediator release,in animal and human models of asthma

A most active biologue of disodium cromoglycate (DSCG) available, lodoxamide tromethamine (LT), has been studied and characterized pharmacologically, in animal and human models of asthma. It has self-tachyphylaxis, but has oral activity (lodoxamide ethyl) in rats, primates, and man. In rats (LT) was 2,500× more active than DSCG (ID₅₀=0.001 mg/kg), in primates the drug was also active by several routes (inhalation 1 g/kg, IV 0.001 mg/kg, and oral 10 mg/kg). In isolated rat peritoneal mast cells, the compound displayed a biphasic dose response inhibition to histamine release initiated by (48/80, anti-IgE, and the calcium ionophore A23,187) with IC₅₀ values of 0.1–50 M. The consistent finding relating to its mode of action was its ability to inhibit⁴⁵calcium flux into the mast cell in response to antigen or A23,187.Clinical evaluations of lodoxamide tromethamine showed that at aerosol doses of 1.0 mg or less, it demonstrated significant inhibitory activity against antigen or exercise induced bronchospasm. However, in pilot evaluation studies in clinical asthma settings, the compound could not be shown to spare bronchodilator usage, relative to placebo, or be shown to be more effective than placebo treated patients based on other clinical endpoints. The reason for rat and primate models not being predictive for human long-term clinical asthma in the characterization of anti-release compounds is not known.     

An antiallergic activity of disodium cromoglycate unrelated to mast cell activation

The pharmacological effects of disodium cromoglycate (DSCG) were studied in rats during the development of reactions to various allergens or carrageenin. DSCG (10 mg/kg and 100 mg/kg, i.v.) showed pronounced inhibitory effects on type I and type III (passive Arthus) allergic reactions. An immunological degranulation of mast cells and a significant decrease in tissue histamine content were observed in type I allergic reactions but not in type III allergic reactions characterized by an apparent infiltration of neutrophils. An antihistaminic agent, promethazine (1 mg/kg, i.v.) was effective only against type I allergic reactions and totally ineffective against type III allergic reactions. Thus, the results obtained above strongly suggest that DSCG exhibits at least two mechanisms of antiallergic action; one is related to mediator release from mast cells and the other is unrelated to mast cell activation.     

Gastric histamine content and gastric ulcer formation in cold/restraint stressed rats: Effects of cinnarizine and flunarizine

The effects of the calcium channel blockers cinnarizine (20 mg/kg p.o.) and flunarizine (10 mg/kg p.o.) on gastric and small intestine histamine content and ulcer formation were determined in cold/restraint stressed rats (4°C for 3 h). The effects of cimetidine (100 mg/kg p.o.) were studied for comparison. After the stress, a significant increase (+27%) in gastric histamine content concomitant with gastric ulceration was observed. Pretreatment with cinnarizine or flunarizine restored histamine to the control value and reduced both the incidence (–22% and –44% respectively) and the severity (-nearly 35%) of gastric ulcers. Neither marked changes in histamine content nor mucosal lesions were detected in the small intestine. The effects of cinnarizine and flunarizine resembled those of cimetidine. The obtained data suggest a possible relation between the decrease in the elevated histamine content in stressed rats and the protection against ulcer formation exerted by cinnarizine and flunarizine.     

Characterization of FPL-52694 [5-(2-hydroxypropoxyl)-8-propyl-4-oxo-4H-benzopyran-2-carboxylic acid Na] on histamine release from rat peritoneal mast cells induced by antigen,compound 48/80 and A 23187

We studied thein vitro effects of FPL-52694 [5-(2-hydroxypropoxyl)-8-propyl-4-oxo-4H-benzopyran-2-carboxylic acid Na] on histamine release from rat peritoneal mast cells. These cells exposed to ascaris antigen, compound 48/80 or the ionophore A 23187 concentration-dependently released histamine. About a 30–40% histamine release was obtained by 1×10^–4 g/ml of antigen, 1×10^–7 g/ml of compound 48/80 and A 23187. FPL-52694 (10^–9–10^–4 g/ml) concentration-dependently inhibited the histamine release from mast cells in response to antigen (1×10^–4 g/ml) and compound 48/80 (1×10^–7 g/ml), but only slightly inhibited the histamine release induced by A 23187 (1×10^–7 g/ml). Similar results were obtained with disodium cromoglycate (DSCG), in the same dose ranges. However, the inhibitory activity of FPL-52694 on histamine release by antigen and compound 48/80 was approximately 10 times more potent than that of DSCG at certain coincentrations. Tachyphylaxis was observed when these two agents were preincubated with mast cells for 10 min. These results show FPL-52694 to be a novel mast cell stabilizer.     

The role of mast cell-derived histamine in the closure of an in vitro wound

We have previously reported that mast cells (MC) stimulate 3T3 fibroblast migration and proliferation into an in vitro model of wound obtained by producing in a confluent 3T3 monolayer, a midline cut and by scraping the cells from half of the monolayer. The purpose of the present study was to determine the contribution of mast cell-derived histamine to this MC increasing effect. Histamine levels in supernatants of MC/3T3 cultures unactivated or activated with either compound 48/80 or anti-IgE antibodies (10 min) did not correlate to the degree of fibroblast migration and proliferation into the wound space (42h). Various concentrations of histamine were added to 3T3 fibroblast monolayers in the absence of cocultured MC, and fibroblasts beyond the wound line were counted (42 h). Addition of 100 ng/ml histamine had the highest stimulating effect on fibroblast numbers. This effect was abrogated by the addition of cimetidine (an H-2 antagonist). Addition of cimetidine to unactivated MC/3T3 cultures did not affect the increasing activity of MC presence on the wounded monolayer, although it diminished the enhancing effect obtained after MC activation with compound 48/80. These results indicate that histamine is partially responsible for the mast cell enhancing effect on fibroblast migration and proliferation in an in vitro model of wound.accepted by W. Lorenz     

Effects of thiazinamium chloride on histamine release from rat peritoneal mast cells and on phosphodiesterase activity in guinea pig lung

The effect of thiazinamium Cl (TCl) on histamine release from rat peritoneal mast cells (RPMC) was investigated. Although TCl inhibited compound 48/80-induced histamine release moderately (IC50 value 40 microM), the drug was a weaker inhibitor of ovalbumin-induced histamine release (100 microM, -21%). In contrast, promethazine HCl (PHCl) was more effective against antigen-induced histamine release (IC50 value 13 microM) than against compound 48/80-induced histamine release (100 microM, -53%). Disodium cromoglycate (DSCG) was effective against both antigen and compound 48/80-induced release of histamine with IC50 values of 7 and 1 microM, respectively. Neither TCl nor DSCG at 1 mM increased spontaneous release of histamine from RPMC, whereas PHCl induced spontaneous release by over 50% at 1 mM. TCl did not inhibit phosphodiesterase (PDE) activity in guinea pig lung at 1 mM, whereas theophylline and DSCG inhibited PDE with IC50 values of 1.1 and 0.32 mM, respectively. These data suggest that high local concentrations of TCl may reduce histamine release during an asthmatic attack and improve its effectiveness as a bronchoprotectant.     

Inhibition of allergic reactions by a new antiallergic drug, LC-6 (trans-2,3b,4,5,7,8b,9,10-octahydronaphthol[1,2-c:5,6-c'] dipyrazole). I. Inhibition of the rat reaginic passive cutaneous anaphylaxis.

A new synthetic compound, LC-6, has been shown to inhibit the passive cutaneous anaphylaxis reactions induced in rats by mouse reaginic antibody. In this system, the ED50 was 35 mg/kg body weight of LC-6 administered per os. LC-6 prevented neither histamine skin reactions nor the reactions to histamine and other chemical mediators released by 48/80. Therefore, its inhibitory activity is comparable to that of the model anti-allergic compound, disodium cromoglycate (DSCG). In contrast to DSCG, the new drug exhibits the distinct advantage of being active per os and over prolonged periods of time. Its activity has been shown to persist for at least 6 h when doses 4 times higher than the ED50 were administered. The duration of the drug effect was clearly dose-dependent. Predoses of the compound increased its effectiveness. The long-lasting association of LC-6 with mast cells, as indicated by its prolonged inhibitory activity, makes it a valuable tool in the search for receptors involved in anaphylactic reactions.     

Amaranthus spinosus Linn. inhibits mast cell-mediated anaphylactic reactions

The current study characterizes the mechanism by which the Amaranthus spinosus (Amaranthaceae) decreases mast cell-mediated anaphylactic reactions. Anaphylaxis is a typical hypersensitivity Type I reaction, sharing common mechanisms with asthma in its early and late phases. Mast cells are key as effector cells in hypersensitivity Type I reactions. A. spinosus has been traditionally used in the treatment of allergic bronchitis and asthma, but its role in mast cell-mediated anaphylactic reactions has not fully been investigated. This report investigated the potential effects of the ethyl acetate fraction of A. spinosus leaves (EAFAS) against a compound 48/80 (potent secretagogue)-induced systemic anaphylactic shock paradigm in a mouse model. In addition, rat peritoneal mast cells (RPMC) were used in in vitro studies to investigate the effect of EAFAS on compound 48/80-induced peritoneal mast cell degranulation and histamine release. When administration by the oral route-1 h before compound 48/80 injection-EAFAS (at dose from 0.001-1 g/kg) completely inhibited the induced anaphylactic shock. EAFAS at concentrations ranging 0.25-1 mg/ml dose-dependently attenuated rates of mast cell degranulation and histamine release from RPMC that were evoked by compound 48/80. The results of the present investigation indicated that EAFAS stabilizes the mast cell lipid bilayer membrane, thereby preventing the perturbation of membrane and the release of histamine. As a result of these anti-degranulating and anti-histaminic effects, it can be suggested that EAFAS may have a potential use in the prophylaxis and management of anaphylactic reactions.     

Effects of N-556 on experimental allergy models in rats

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

A protective action of disodium cromoglycate against the contraction of guinea-pig ileum induced by various pharmacological stimulants

The effect of disodium cromoglycate (DSCG) on the contraction of isolated guinea-pig ileum induced by histamine, acetylcholine and serotonin has been investigated. DSCG protected ileum against all agents tested. The action of DSCG at concentrations of 10^–3 to 10^–2 M was both dose- and time-dependent. Furthermore, DSCG inhibited compound 48/80-induced histamine release from isolated mast cells over the same range of concentrations.The anti-histaminic action of DSCG was reversible and after 2 h the ileum responded normally to histamine.DSCG-induced inhibition of the contractile response to histamine could be overcome by increasing concentrations of histamine but not by extracellular calcium.A mechanism of the action of DSCG, either against the contraction of ileal smooth muscle or against histamine release from mast cells, is discussed with a view to the inhibition of the utilization of calcium ions by both cells.This work was supported by the Polish Academy of Sciences, Grant No. 10.5.     

Effects of drugs combining H1 and H2 receptor antagonist activity on histamine release and life threatening anaphylactoid reactions in pigs

Summary Two recently synthetized drugs combining H1- and H2-receptor antagonist activity in a single molecule (alitidine, clophetidine) were compaired for their potency in preventing histamine release and lifethreatening anaphylactoid reactionin vivo with the usually tested H1/H2-blocker combination dimetindene/cimetidine. Saline premedication in a fourth group served as control. Anaesthetized and ventilated pigs were administered H1/H2-blockers or placebo and 500 ml of blood were removed. Subsequently, 500 ml saline solution containing 1 mg/kg compound 48/80 for initiating histamine release were rapidly reinfused (n=15 pigs per group). The system proved reliable in creating hypotension and histamine release in the placebo group. The extent of histamine release did not differ between the placebo, alitidine and dimetindene/cimetidine groups. However, clophetidine was shown to be effective in preventing increases in plasma histamine after compound 48/80. Tachycardia was almost completely prevented by dimetindene/cimetidine, was diminished by clophetidine, but was not affected by alitidine. Hypotension following 48/80 was best reversed by clophetidine. This investigation suggests that clophetidine is a most promising drug in preventing histamine release and its circulatory effects in a pig anaphylactoid shock model. It requires, however, further quantitative confirmation in experiments with a two-group design only, since the analysis of variance is less suitable for the extreme variation of the plasma-histamine values after administration of compound 48/80.