Beta-adrenoceptors invloved in inhibition of histamine release from sensitized guinea-pig lung.

Selective β-adrenoceptor agonists and antagonists were used to study the type of β-adrenoceptors involved in inhibiting antigen-induced histamine release from actively sensitized guinea-pig lung. Results obtained with six non-catechol β-adrenergic agonists were compared with those found in guinea-pig atrial (β₁) and tracheal (β₂) preparations. In terms of rank order the relative activities of the compounds differed in the three preparations. Dissociation constants (K_B values) for the cardioselective antagonist H93/26 were assessed using (?)-isoprenaline as an agonist. The K_B value for inhibition of histamine release was significantly different from, and intermediate between, the K_B values obtained in atria and trachea. In the guinea-pig tissues H35/25 was not a selective β-adrenoceptor antagonist; K_B values were not significantly different in the three preparations. The results using the β-adrenoceptor agonists and antagonists suggest that the β-receptors involved in inhibition of antigen-induced histamine release in the guinea-pig lung differ from those found in guinea-pig atria and trachea.     

Antigen-induced contraction of guinea-pig trachea: search for mediator release with cascade superfusion bioassay.

Ovalbumin induces contraction of sensitized guinea-pig trachea, both in the presence and absence of indomethacin. Cascade superfusion bioassay was employed to detect mediator release. A prostaglandin E-like material was released in response to antigen in the absence of indomethacin but, no biologically active material could be detected from trachea in the presence of indomethacin. Thus the substance responsible for antigen-induced tracheal contraction, although appearing to be a lipoxygenase product, is as yet undefined.     

Immune release of histamine and other lipid mediators from guinea-pig isolated kidney: antagonism by BN-52021.

The ability of a specific PAF-receptor antagonist, BN-52021, to control the release of mediators of anaphylaxis from actively sensitized (ovalbumin) guinea-pig has been investigated "in vitro". BN-52021 perfused through the kidney at different molar concentrations (1 x 10(-4)-1 x 10(-5)-1 x 10(-6] prior to antigen challenge neither modified the basal values of perfusion pressure nor stimulated mediator release from the organ. On the contrary, the compound antagonized in a concentration dependent way both vasoconstriction of the renal vessels and the increase in the perfusate of histamine, TXB2 and SRS-A due to antigenic shock. The antagonistic activity of BN-52021 was very consistent at 1 x 10(-4) M at which concentration the immunological release of histamine and TXB2 was reduced by 75%. The beneficial effect of BN-52021 in experimental anaphylaxis of the kidney may have some therapeutic implications principally in those pathological conditions where an abnormal increase of renal histamine and other mediators may compromise the haemodynamic function of this organ.     

The PAF-acether receptor antagonist BN-52021 inhibits mediator release during guinea-pig active lung anaphylaxis

An anaphylactic reaction was induced with the specific antigen (1 mg Ovalbumin) in perfused lungs from actively sensitized guinea-pigs in order to evaluate the ability of the ginkgolide BN-52021 (0.4, 4, 40 micrograms/ml) to modulate the mediator release. The ginkgolide reduces in a dose dependent manner the release of histamine (22%, 45% and 75% of inhibition), TXB2 (77% of inhibition at the maximal dose used) and of SRS-A to a lower extent (only 33% at the higher dose). BN-52021 was still powerful in reducing histamine release induced by immunological reaction in indomethacin treated animals. In conclusion, the present "in-vitro" results confirm the beneficial activity of this ginkgolide, already demonstrated by the same Authors in "in-vivo" experiment, in anaphylactic reactions, and further substantiate the wider spectrum of action of the ginkgolide beside its specific PAF receptor antagonistic activity.     

Endothelin-induced contraction and mediator release in human bronchus.

1. To elucidate the role of acetylcholine and various autacoids in endothelin-1 (ET-1)-induced contraction in human bronchus, the effects of various receptor antagonists were examined. In addition, the ability of ET-1 to stimulate the release of histamine, peptidoleukotrienes and prostanoids was determined. 2. ET-1 was a potent and effective contractile agonist in human bronchus, possessing similar potency and efficacy to leukotriene D4 (LTD4); EC50 (-log M): ET-1 = 7.76 +/- 0.09, n = 7; LTD4 = 8.46 +/- 0.53, n = 7; P > 0.2; maximum response (% 10 microM pre-carbachol): ET-1 = 103.8 +/- 17.4, n = 7; LTD4 = 95.5 +/- 9.3, n = 7; P > 0.6. 3. The cyclo-oxygenase inhibitor, sodium meclofenamate (1 microM) or the potent and selective thromboxane receptor antagonist, SQ 29,548 (1 microM) were without significant effect on ET-1 concentration-response curves. 4. In the presence of sodium meclofenamate (1 microM), the muscarinic receptor antagonist, atropine (1 microM), the platelet activating factor (PAF) receptor antagonist, WEB 2086 (1 microM) or the combination of the H1-histamine receptor antagonist, mepyramine (10 microM) and the leukotriene receptor antagonist, SK&F 104353 (10 microM), were without marked effect on ET-1 concentration-response curves. In addition, the combination of all four receptor antagonists did not antagonize ET-1-induced contraction. 5. ET-1 (0.3 microM) did not stimulate the release of histamine or immunoreactive leukotrienes from human bronchus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of the release of various mediators from atrial and ventricular tissues of sensitized guinea-pig hearts

By comparison with ventricular tissues, collagenase-dispersed cell suspensions obtained from atrial tissues of sensitized guinea-pigs showed a higher histamine content, a higher proportion of mast cells, and a higher release with antigen or antisera to IgG, IgG1 and IgG2 of the following mediators: histamine, thromboxane B2 and leukotriene C4.     

Autoradiographic localization of beta-adrenoceptor subtypes in guinea-pig kidney.

The distribution of beta-adrenoceptor subtypes in slide-mounted sections of guinea-pig kidney has been examined by the technique of in vitro labelling combined with autoradiography. Binding of (-)-[125I]-cyanopindolol (Cyp) to kidney sections equilibrated and dissociated slowly, was saturable and stereoselective with respect to the isomers of propranolol and pindolol. These characteristics were appropriate for binding to beta-adrenoceptors. Delineation of beta-adrenoceptor subtypes was achieved by use of betaxolol (beta 1-adrenoceptors) and ICI 118,551 (beta 2-adrenoceptors) and computer assisted curve fitting techniques. Both beta 1- and beta 2-adrenoceptors were present in the proportions 1:2. 3H-Ultrofilm images of (-)-[125I]-Cyp binding to guinea-pig kidney sections showed localized patches of binding in the cortex and concentrated binding in the outer stripe of the medulla. Cortical receptors were of the beta 1 subtype and those associated with the outer stripe of the medulla were of the beta 2-adrenoceptor subtype. beta 1-Adrenoceptors were concentrated over glomeruli and beta 2-adrenoceptors over the straight portion of the proximal tubule.     

Hypoxia modulates mediator responses and neurotransmission in guinea-pig trachea in vitro

To discover whether hypoxia affects mediator responses and neurotransmission in tracheal smooth muscle, we studied in vitro tracheal segments from guinea-pigs under isometric conditions. Hypoxia itself did not alter the basal tone. The maximum response to acetylcholine and histamine under hypoxia was less than that under oxygenated conditions. The logarithm of 50% effective concentration (log EC₅₀) of the response to acetylcholine under hypoxia was not altered, but the log EC₅₀ of the response to histamine decreased significantly. In contrast to the response to exogenous acetylcholine, the maximum contractile response to electrical field stimulation (EFS) under hypoxia was not different from that under oxygenated conditions, but the logarithm of 50% effective frequency of contractions caused by EFS under hypoxia decreased significantly. On the other hand, non-adrenergic-non-cholinergic relaxation caused by EFS was unaffected by hypoxia. These observations suggest that hypoxia can modulate the responses of tracheal smooth muscle to acetylcholine, histamine and nerve stimulation.     

Role of thromboxane A2, leukotriene C4 and histamine in the antigen-induced vasoconstriction in perfused, sensitized guinea-pig kidney

The existence of a role for TXA2, histamine, and possibly LTC4 in the antigen-induced renal vasoconstriction in isolated, perfused kidney of sensitized guinea-pigs is demonstrated.     

Substance P and Arg-Pro-Lys-Pro-NH-C12-H25-induced mediator release from different mast cell subtypes of rat and guinea-pig

Histamine was released from mast cells in isolated perfused heart and kidney of the rat, but not from mast cells in guinea-pig tissues, by a substance P (SP) analogue (SP(1-4)-NH-C12H25), SP(1-4)-C12 for abbreviation. This peptide also released histamine from peritoneal mast cells and basophil leucocytes of the rat. Substance P itself was compared with SP(1-4)-C12 and some structurally related peptides and showed weaker activity. SP(1-4)-C12 also released leukotrienes C4, D4, E4 and thromboxane B2 from rat heart. However, there was little effect on heart rate and force of contraction and no effect on perfusion pressure (vascular resistance) of either rat heart or kidney. The findings demonstrate the structural requirements for histamine release by SP (a possible mediator of 'neurogenic' inflammation), the metabolic energy-dependence of the release process and the functional heterogeneity and interspecies differences in mast cell populations.     

Paf-induced release of spasmogens from guinea-pig lungs.

1. The injection of platelet activating factor (Paf; 250 ng), leukotriene B4 (LTB4; 50 ng) and leukotriene D4 (LTD4; 10 ng) elicited contractions of strips of guinea-pig trachea, bronchus and lung parenchyma. 2. When the effluent of perfused guinea-pig lungs was superfused over strips of guinea-pig trachea, bronchus and parenchyma, the intra-arterial injection of Paf (250 ng) caused the release of spasmogen(s) which contracted all three tissues. 3. The infusion of indomethacin (10 micrograms ml-1) into the pulmonary artery and over the assay tissues inhibited the responses of the tissues to the effluent of the lungs stimulated by Paf (250 ng) and LTB4 (50 ng). However, treating only the assay tissues with indomethacin (10 micrograms ml-1) did not block the contractile responses to the effluent of the lungs stimulated with LTB4 or Paf. stimulated with Paf. 4. Pretreatment of the lungs with indomethacin (10 micrograms ml-1) or aspirin (30 micrograms ml-1) for 30 min, washing them out and suspending them over the assay tissues did not block the release of spasmogens elicited by Paf but appeared to inhibit the release of cyclo-oxygenase products. 5. The infusion of two lipoxygenase inhibitors, nordihydroguaiaretic acid (NDGA; 1 microgram ml-1) and L-655,240 (1 microgram ml-1), into the pulmonary artery completely blocked the release of spasmogen(s) from the perfused lungs. 6. The slow reacting substance of anaphylaxis (SRS-A) antagonist, FPL-55712 (10 ng ml-1), did not block the responses of the tissues to the spasmogen(s) release by Paf. 7. The infusion of the Paf antagonist BN-52021 (30 micrograms ml-1) into the pulmonary artery completely abolished the release of spasmogen(s) induced by Paf. 8. These data suggest that a lipoxygenase product, possibly LTB4, could be responsible for the spasmogenic activity released by the lungs following Paf stimulation. Cyclo-oxygenase products released following Paf stimulation appear to result from the initial LTB4 generation.     

The effects of Haemophilus influenzae vaccination on anaphylactic mediator release and isoprenaline-induced inhibition of mediator release

The influence of Haemophilus influenzae on anaphylactic mediator release from ovalbumin-sensitized isolated guinea pig lungs was investigated. Lungs from H. influenzae-vaccinated animals released prostaglandins and thromboxanes following a smaller dose of ovalbumin than was effective in non-vaccinated animals. Histamine release was significantly increased in 4 day-vaccinated animals but not 1 or 10 days after vaccination, while broncho-constriction was potentiated in 1 and in 4 day-vaccinated animals. This increased histamine release was achieved following 2 micrograms ovalbumin. In contrast, doses of 10 micrograms and 1 mg ovalbumin respectively did not affect and decreased histamine release in the vaccinated group. The inhibition of anaphylactic mediator release by an infusion of 6 x 10(-9) M isoprenaline was significantly attenuated by H. influenzae vaccination. These results indicate an increased sensitivity to antigenic challenge and suggest that the functioning of beta-adrenoceptors was decreased as a result of H. influenzae vaccination.     

New approaches to analysis of the interrelationship between cholinergic and dopaminergic mediator systems

Intermediatory relationships between the cholinergic and dopaminergic neurotransmission systems were analyzed using published data and the original experimental results obtained on Daphnia magna Straus, a new test object. Based on these results, the antihaloperidol activity of a series of M- cholinoblocking agents with different receptor selectivities were studied in comparison to the new cholinoblocker pentifin exceeding in the activity the classical antiparkinsonian drugs such as cyclodol, amedin, and norakin.     

Change in the activity of the cyclic AMP-dependent protein kinase in antigen-stimulated sensitized mast cells and effect of drugs inhibiting allergic mediator release

The activity of cyclic AMP-dependent protein kinase (protein kinase A) in the sensitized rat mast cell was decreased 2 min after antigen challenge when the histamine release exhibited a maximum. Drugs inhibiting allergic mediator release such as disodium cromoglycate, tranilast and theophylline significantly inhibited antigen-induced histamine release and reduced a decrease in the activity of protein kinase A. These results suggest that protein kinase A is involved in the histamine releasing process in the mast cell, and drugs inhibiting allergic mediator release cause their effects partially through the inhibition of protein kinase A.     

Release of arachidonic acid metabolites and histamine from sensitized guinea-pig lung following antigen challenge.

1. The time course of mediator release and the hypothesis that the ratio of eicosanoids to histamine might alter with the intensity of stimulus or its route of administration has been explored in isolated perfused lung from sensitized guinea-pigs challenged with ovalbumin. 2. Histamine and prostaglandin release was rapid in onset and virtually complete within 10 min. Thromboxane B2 (TXB2) and leukotriene D4 (LTD4) release, however, was more sustained. Release of the major prostanoid metabolites was relatively delayed compared to that of the parent compounds and was more sustained. 3. Mediator release was antigen-dose dependent and TXB2, prostaglandin D2 (PGD2) and LTD4 release linearly related to histamine concentrations (P less than 0.05). However, the ratio of the percentage maximum release of eicosanoids relative to histamine was greatest with low doses of ovalbumin. 4. At a low antigen dose (10 micrograms ovalbumin), histamine and prostanoid release was greatest when the challenge was via the airway rather than into the pulmonary artery and the greatest differences were in PGF2 alpha levels. At near maximal challenge (1 mg ovalbumin) there was little difference in concentrations of PGD2, TXB2, 6-oxo-PGF1 alpha and LTD4 by either route, but PGF2 alpha levels remained greater. 5. The results indicate that biologically active amounts of prostanoids may be released from sensitized lung at low degrees of mast cell activation and that differences in mediator release following antigen administration to the airway or into the pulmonary vasculature simply reflects its accessibility to sensitized cells.     

Non-immunological release of slow-reacting substance from guinea-pig lungs.

1 During incubation with calcium ionophore A23187, sensitized and unsensitized guinea-pig chopped lung released a slow-reacting substance (SRS) and histamine. 2 SRS possessed many characteristics of slow-reacting substance of anaphylaxis (SRS-A). It was inactivated by arylsulphatase, antagonized by FPL55712 (1 microgram/ml) and more stable in alkali than acid. Furthermore, it behaved like SRS-A by stimulating archidonic acid metabolism in guinea-pig isolated perfused lungs. 3 Maximal ionophore generation of SRS in sensitized lung was greater than maximal anaphylactic generation of SRS-A but the release of histamine was not significantly different. Simultaneous challenge with antigen and ionophore produced more SRS-like or SRS-A-like activity than either stimulus alone. 4 These results have shown a non-immunological release from guinea-pig lung of SRS which was similar (or possibly identical) to SRS-A. It is suggested that in addition to mast cells, other cell types may be involved.     

Ischemia reperfusion injury and histamine release in isolated and perfused guinea-pig heart: pharmacological interventions.

Experiments were carried out to provide further information on the biochemical and morphological changes occurring in the guinea-pig heart after multiple ligature and reopening of the left anterior descending (LAD) coronary artery. In isolated perfused guinea-pig heart the reopening of LAD coronary artery leads to a release of histamine related to a loss of metachromasia by cardiac mast cells. The process is associated with malonyldialdehyde (MDA) production, cellular overload of calcium and ventricular arrhythmias which can be modulated by pharmacological interventions.     

Mediators of adenosine- and ovalbumen-induced bronchoconstriction of sensitized guinea-pig isolated airways

The mediators of bronchoconstriction of isolated lungs and trachea from ovalbumen sensitized guinea-pigs to adenosine and ovalbumen were examined using relevant antagonists. Changes in perfusion pressure and tension of paired lung halves and tracheal spiral strips, respectively, were recorded in response to adenosine (1 mM lung, 300 microM trachea), histamine (10 microM), methacholine (10 microM) and ovalbumen (10 microg). One half was perfused with antagonist while the other received vehicle. Tracheal strips were superfused throughout with the P(1) receptor antagonist 8-phenyltheophylline, to examine 8-phenyltheophylline-resistant responses. The histamine H(1) receptor antagonist, mepyramine (1.5 mM), the cyclooxygenase inhibitors, indomethacin (5 mM) and diclofenac (5 mM), the leukotriene receptor antagonist, zafirlukast (1 mM), and the lipoxygenase inhibitor, zileuton (20 mM), alone failed to inhibit bronchoconstriction by adenosine and ovalbumen of the lung and trachea. When two antagonists were combined, only mepyramine and zafirlukast significantly reduced the lung responses to adenosine and ovalbumen. The tracheal adenosine response was substantially reduced, although not significantly, while ovalbumen was significantly reduced. When mepyramine, indomethacin and zafirlukast were combined, the lung constriction by adenosine and ovalbumen were virtually abolished. Similarly, the combination of mepyramine, diclofenac and zafirlukast significantly attenuated the lung responses to adenosine and ovalbumen. Thus, histamine, cyclooxygenase products and leukotrienes alone are not responsible for the bronchoconstriction of isolated sensitized lung tissues to adenosine or ovalbumen, which appears to be due to the release of all three mediators.