Release Of SRS-A Research Articles

The effect of Ro 21-7634 on the antigen-induced production of bronchoconstrictive arachidonic acid metabolites in the guinea pig lung.

Ro 21-7634 has previously been shown to inhibit histamine and SRS-A release from actively-sensitized guinea pig lung fragments upon antigen challenge. In the studies described herein, it was observed that Ro 21-7634 does not decrease SRS-A release but instead acts to inhibit the synthesis of this mediator. This was confirmed by studying SRS-A synthesis in vitro in rat peritoneal cells after challenge with ionophore A23187. In the peritoneal cell system, Ro 21-7634 exhibited an IC50 of 500 microM, in comparison with 5.8,11,14-eicosatetraynoic acid, phenidone and BW755C (IC50's of 2, 100, and 100 microM, respectively). When studied at 10(-4) and 10(-3) M in perfused guinea pig lung, Ro 21-7634 inhibited antigen-induced thromboxane A2 production by 68 and 96%, respectively. In this system, antigen is believed to induce thromboxane A2 production through the release of histamine and SRS-A from lung tissue. These mediators then interact at receptor sites in the lung parenchyma to induce thromboxane A2 synthesis. Ro 21-7634 could thus be inhibiting thromboxane A2 production by preventing the release of histamine and synthesis of SRS-A in the perfused lung system. Such a mechanism is suggested by the fact that although Ro 21-7634 was effective in inhibiting antigen-induced thromboxane production, it was ineffective in inhibiting thromboxane A2 production induced in the guinea pig lung system by the direct perfusion of histamine or SRS-A through the lung.

In vitro studies on the mechanism of action of a new antiallergic, Ro 21-7634.

The effects of Ro 21-7634 and disodium cromoglycate (cromoglycate) on the in vitro release of mediators of anaphylaxis from rat peritoneal cells and guinea pig lung tissue were compared. Ro 21-7634 was 25 fold more potent than cromoglycate as an inhibitor of antigen-induced histamine release from passively sensitized (IgE) rat peritoneal cells. Ro 21-7634 was also the more potent inhibitor of both compound 48/80- and concanavalin A-induced histamine release from rat peritoneal cells. The two drugs shared the common properties of producing the same maximal level of inhibition in each of the above releasing systems and exhibiting a time and concentration dependent loss of inhibitory activity when added to the cells prior to the releasing agent. Neither drug inhibited ionophore A23187-or ionophore X537A-induced histamine release from these cells. Ro 21-7634 inhibited antigen-induced (IgG1) histamine and SRS-A release from actively sensitized guinea pig lung fragments, whereas cromoglycate did not. The results indicate that Ro 21-7634 and cromoglycate act through a common mechanism to inhibit allergic mediator release and that Ro 21-7634 is the more potent inhibitor.

The role of calcium in the generation of intracellular SRS-A in passively sensitized human lung challenged with antigen.

Calcium deprivation inhibits the formation and subsequent release of SRS-A as well as histamine from passively sensitized human lung fragments challenged with antigen. Antimycin A inhibits the release of histamine and SRS-A in a dose dependant fashion, while causing a mild inhibition of SRS-A formation throughout the dose range studied. These data suggest that the influx of calcium is the critical event for the generation of SRS-A within the cell.

The role of arachidonate lipoxygenase in the release of SRS-A from guinea-pig chopped lung

The immunological release of SRS-A was investigated in guinea-pig chopped lung. A number of unsaturated fatty acids, all of which are substrates for arachidonate lipoxygenase were found to potentiate the release of SRS-A. This potentiation was enhanced by indomethacin, a cyclo-oxygenase inhibitor, and completely reversed by nordihydroguaiaretic acid (NDGA) and eicosatetraynoic acid (ETA) which inhibit lipoxygenase. This suggests that some aspect of arachidonate lipoxygenase action stimulates release of SRS-A and that release of SRS-A is increased by redirection of arachidonic acid (AA) metabolism via the lipoxygenase pathway (Hamberg, 1976). However, although exogenous 14C-AA increased SRS-A output it was not incorporated into SRS-A.

Release of mediators from free bronchoalveolar cells: effect of ionophore A23187 and antigen challenge.

The ionophore A23187 stimulated the release of prostaglandins and SRS-A (now identified as leukotriene D4) from guinea-pig bronchoalveolar macrophages. Upon specific antigen challenge of the cells obtained from ovalbumin-sensitized animals or of normal cells preincubated with the serum of sensitized animals, prostaglandins, SRS-A or histamine were undetectable. Furthermore, treatment of "sensitized" cells with the ionophore resulted in a reduced liberation of prostaglandins in comparison to control cells. It is suggested that sensitization produce in bronchoalveolar macrophages some functional alterations of arachidonic acid oxygenation products.

Effects of drugs on the acute inflammation following intraperitoneal injection of antigen into actively sensitised rats.

When actively sensitised rats were injected intraperitoneally with antigen, the local reaction that ensued can be divided into two phases: an immediate reaction characterised by histamine and SRS-A release with an associated extravasation of plasma proteins, and a later reaction involving infiltration of neutrophilic polymorphonuclear leucocytes. When the immediate reaction was modified by BRL 10833 (which inhibits histamine release from rat mast cells and reduces extravasation of plasma proteins), there was no reduction in neutrophil infiltration. FPL 55712, an SRS-A antagonist, also failed to inhibit neutrophil infiltration. The beta-adrenoreceptor stimulants isoprenaline and salbutamol reduced neutrophil infiltration. Isoprenaline inhibited the extravasation of plasma proteins when given before antigen, but even when administered to rats after antigen, when extravasation was complete, it still inhibited neutrophil infiltration. Propranolol reversed isoprenaline-induced inhibition of neutrophil infiltration.

The mechanism of enhancement by fatty acid hydroperoxides of anaphylactic mediator release

Indomethacin augmented the release of histamine and SRS-A but abolished synthesis of TxB 2. Compound CLI that inhibited both cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism did not augment release of anaphylactic mediators. 13-HPLA enhanced mediator release from lungs in which arachidonic acid metabolism was blocked by compound CLI. Thus, it is concluded that 13-HPLA enhances mediator release not by altering the balance of arachidonic acid metabolites, e.g. by inhibiting synthesis of prostacyclin, but by a direct effect on lung mast cells. A corollary to this conclusion is that the fatty acid hydroperoxide (HPETE) formed by lipoxygenase from arachidonic acid may also augment the release of anaphylactic mediators. Thus, the enhancement of mediator release by indomethacin may be attributed to increased synthesis of HPETE following inhibition of cyclo-oxygenase.

A POSSIBLE MODULATORY ROLE FOR PROSTACYCLIN (PGI2) IN IgGa‐INDUCED RELEASE OF SLOW‐REACTING SUBSTANCE OF ANAPHYLAXIS IN RATS

Antigen challenge in vivo of rat peritoneal cells (enriched with monocytes and polymorphonuclear leucocytes) passively sensitized 2 h previously with homologous antibody of the IgGa class released large amounts of slow-reacting substance of anaphylaxis (SRS-A, 1739 +/- 59 u/ml) into the peritoneal fluid. This reaction was strongly inhibited by prostacyclin (PGI2, ED50 = 0.5 microgram/kg i.p.) and by isoprenaline (ED50 = 0.2 microgram/kg i.p.) but prostaglandins E1, E2 and 6-oxo-prostaglandin F1alpha were only weak inhibitors. Indomethacin (10 mg/kg, orally) augmented by 30% the release of SRS-A, whereas thromboxane B2 (50 microgram/kg i.p.) had no effect. Lowering the antigen (ovalbumin) dosage from 400 microgram/ml to 10 microgram/ml reduced the control release of SRS-A by 70% and increased the inhibitory effect of prostaglandins I2, E1 and isoprenaline. Augmentation of release by indomethacin remained unchanged. These preliminary data suggested that endogenous prostacyclin may modulate the anaphylactic release of SRS-A from rat peritoneal cells.

The pharmacology of prostaglandin-like substances released from guinea-pig lungs during anaphylaxis

The pharmacology of the prostaglandins (PGs) and thromboxanes (Txs) released from immunologically challenged guinea-pig lungs is related to their roles in the anaphylactic response. 6-oxo-PGF 1α probably contributes substantially to bronchoconstriction during anaphylaxis. TxB 2 may contribute to the anaphylactic response by increasing SRS-A release and by stimulating leucotaxis. The 15-oxo metabolites of PGE 2 and PGF 2α are rather weak spasmogens, but might modify respiratory muscle contractions and pulmonary vascular resistance. The 15-oxo 13,14 dihydro metabolites of PGE 2, PGF 2α and TxB 2 were inactive in the systems studied, suggesting an important inactivating role for the 13:14 reductase enzyme.

Effect of disodium cromoglycate and Picrorhiza kurroa root powder on sensitivity of guinea pigs to histamine and sympathomimetic amines.

Four weeks pretreatment with disodium cromoglycate (DSCG) and the powdered roots of the herb Picrorhiza kurroa, Benth, rendered guinea pigs less sensitive to histamine when compared with appropriate controls. The bronchodilator effects of isoprenaline and adrenaline were found to be markedly enhanced. The severity and duration of the allergic bronchospasm was significantly less in animals pretreated with the two drugs. Furthermore, the total histamine content of the lung tissue in animals pretreated with DSCG and P. kurroa was significantly less than that in the untreated controls. The pretreatment was also found to exhibit inhibitory effect on the immunological release of histamine and SRS-A from chopped lungs.

Studies of the antigenicity and allergenicity of phospholipase A 2 of bee venom

The antigenic and allergenic properties of phospholipase A 2 (PLA 2) and whole bee venom were compared by measuring the IgG and IgE antibody responses in animals and man. Precipitating antibodies raised in rabbits and reaginic and other antibodies raised in mice reacted about equally with both bee venom and PLA. The majority of human sera containing bee venom-specific IgE also contained PLA-specific IgE, although in somewhat lower titers. Similarly, most human sera with significant amounts of total antibodies reacting with bee venom also had antibodies reacting with PLA. Histamine and SRS-a release from leukocytes of sensitive patients followed challenge with whole bee venom and PLA in the majority of instances. However, mediator release from several patients' cells was obtained with bee venom only. These studies suggest that although PLA is a major allergen and antigen in bee venom, significant exceptions in patients' reactivity may limit its potential diagnostic and therapeutic usefulness.

Inhibitory effects of various drugs on dual asthmatic responses in wheat flour-sensitive subjects

In order to investigate the mechanism of late asthmatic response (LAR), inhibitory effects of various drugs for LAR were examined in two wheat flour-sensitive asthmatic subjects who showed immediate and late responses in the allergen provocation test and skin test. Antihistamines did not inhibit the LAR but totally or partially inhibited the immediate response. By contrast, corticosteroids inhibited the LAR but not the immediate response. Disodium cromoglycate inhibited both responses. Diethyl carbamazine citrate, an inhibitor of release of SRS-A, seemed to shorten the duration of the LAR, although it has no effect on the immediate response and/or on the severity of the LAR. Indomethacin and acetyl salicylate, which inhibit prostaglandin synthesis, had no significant effects on either the immediate or the LAR.

Tracheal mucous transport in experimental canine asthma.

Tracheal mucous velocity (TMV) was measured in experimental canine asthma. All 10 sensitive dogs exposed to an aerosol of Ascaris suum extract showed a decrease in TMV to about one-third of base-line values within 45 min whereas only half of them (reactors) responded with bronchospasm as measured by a significant reduction in specific respiratory system conductance (SGrs). Mean TMV remained decreased at the end of the 2-h observation period when mean SGrs had returned to base-line values in the reactors. Neither TMV nor SGrs changed in nonsensitive animals who inhaled ragweed antigen. Aerosols of acetylcholine and histamine increased TMV thereby excluding these mediators as responsible for the impairment of mucous transport in asthma. Nebulization of A. suum antigen together with a selective antagonist of slow reacting substance of anaphylaxis (srs-a) produced a marked increase of TMV in all dogs regardless of whether or not bronchospasm was elicited. This suggests that the observed decrease in TMV may be related to the release of SRS-A during the immunologic reaction.

Proceedings: Effect of cromoglycate and eicosatetraynoic acid on the release of prostaglandins and SRS-a from immunologically challenged guinea pig lungs.

Proceedings: Effect of cromoglycate and eicosatetraynoic acid on the release of prostaglandins and SRS-a from immunologically challenged guinea pig lungs.

Minimal Effective Dosage of Cromolyn

To Editor.— Numerous studies have shown that cromolyn sodium is an effective antiasthmatic medicine when used prophylactically on a regular basis. Cromolyn inhibits degranulation of sensitized mast cells that occurs after exposure to specific antigens, and inhibits release of histamine and SRS-A. The manufacturers of cromolyn, and investigators, advise a starting dose of 20 mg (one capsule) four times a day by inhalation, for children 5 years old and over. 1 The manufacturers' brochures state that the dose for adults and children 5 and over is contents of one Aarane capsule inhaled four times daily at regular intervals.... Dykes 2 specifies minimum dosage that is found effective. For this reason, following case illustrates an important point. Report of a Case.— A 5-year-old white boy gave a three-year history of asthma, and had been wheezing almost daily for two years. His wheezing increased with exercise.

Monkey SRS-A

In the present study it was shown that SRS-A, as well as histamine, is released on allergen challenge of fragments of monkey skin passively sensitized with human ragweed allergic serum. Some parameters of SRS-A and histamine release from skin fragments were compared with those of lung. By filtration through Biogel P-2 in aqueous medium it was demonstrated that SRS-A released from lung or skin fragments exists as a molecular size species of about 1,000 daltons, some of which is reversibly bound to macromolecular component(s). On the other hand, SRS-A sieved through Sephadex LH-20 in 80% ethanol had a molecular weight of 350–400 daltons. A comparison was made of the gel filtration properties of SRS-A and several prostaglandins in both gel-solvent systems. The results suggested that 350–400 daltons may closely approximate the actual molecular weight of monkey SRS-A.

IMMUNOLOGICAL RELEASE OF HISTAMINE AND SLOW-REACTING SUBSTANCE OF ANAPHYLAXIS FROM HUMAN LUNG

The sensitization of human lung with atopic serum is both time and temperature dependent. Highly purified IgE myeloma protein is capable of blocking sensitization of human lung with atopic serum whereas myeloma proteins of the IgG subgroups are inactive. Drugs capable of increasing cellular levels of CAMP such as beta-adrenergic agents and methylxanthines inhibit the antigen-induced release of both histamine and SRS-A from human lung and these agents demonstrate synergism when used together. The beta-adrenergic blocking agent, propranolol, prevents epinephrine-induced inhibition of the immunologic release of the mediators. Diethylcarbamazine also inhibits the antigen-induced release of histamine and SRS-A from human lung and a synergism between this drug and epinephrine is observed. Predominantly alpha-adrenergic stimulation achieved by combining propranolol with epinephrine or norepinephrine not only prevented the inhibitory activity of the sympathomimetic amines but also resulted in an enhanced release of histamine and SRS-A. These observations suggest that whereas increases in cellular levels of CAMP are inhibitory, decreases in cellular levels of CAMP enhance the antigen-induced release of the mediators.

Inhibition of Histamine and SRS-A from Monkey Lung Tissue by Chlorophenesin

Summary Chlorophenesin completely inhibited allergen-reagin-induced histamine and SRS-A release from monkey lung tissue. Preliminary studies suggest that chlorophenesin mediates this inhibition by activating adenylcyclase.

Prostaglandin inhibition of the immunologic release of slow reacting substance of anaphylaxis in the rat.

SummaryThe prostaglandins, PGE1 and PGE2, effectively inhibit the IgE- and IgGa-mediated release of SRS-A in the rat in a dose-response fashion. Structure-function studies suggest that the carbonyl group in the 9 position, the position of a double bond in the cyclopentane ring, and either the degree of saturation of the cyclopentane ring or the presence of the hydroxl group in the 11 position, or both, are required for optimal inhibitory activity. Indirect evidence did not establish that prostaglandin inhibition of SRS-A release is mediated through an increase in tissue cyclic AMP levels and no synergism between PGE1 and diethylcarbamazine or diso-dium cromoglycate was demonstrable.

Biologic Properties of Rat Antibodies

Summary Two different classes of rat antibodies have been shown to mediate the i.p. antigen-induced release of histamine. The heat-stable antibodies, associated with IgGa, involved in histamine release could be clearly differentiated from heat-labile homocytotropic antibodies. Antibodies associated with IgGa have been previously shown to mediate the antigen-induced release of SRS-A. It was not possible to dissociate the two biologic activities associated with IgGa antibodies by physical means.