Changes in histamine secretion from mast cells caused by digitalis glycosides

Cardiotonic glycosides modify histamine secretion from rat mast cells in the following way. (1) Preincubation (30 min) of mast cells with liposoluble glycosides (10^–4 mol/l) increases the spontaneous histamine secretion by about 5%. (2) Preincubation of mast cells with 10^–4 mol/l liposoluble glycosides (digitoxine, digoxine, digitoxigenine) decreases histamine release induced by compound 48/80 in the presence of calcium, whereas the water soluble glycoside, strophanthin G, has no effect on the secretion. (3) Preincubation of mast cells in a calcium-free medium with the glycosides (10^–4 mol/l) has a dual-effect on histamine secretion induced by compound 48/80: water soluble glycosides (strophanthin G and K) potentiate histamine release, whereas the liposoluble glycosides (digitoxine, digitoxigenine) decrease the secretory response. The difference in the activity of different glycosides could be explained by their dual effects, namely an inhibition of Na⁺ K⁺-ATPase which leads to an increase in histamine release, and intracellular action(s) of liposoluble glycosides leading to a decrease of histamine secretion.     

Some characteristics of histamine secretion from mast cells treated with ionomycin

The ionophorous antibiotic ionomycin released histamine from rat peritoneal mast cells in both the presence and absence of added calcium ions. The response under the latter conditions was potentiated by brief pretreatment of the cells with chelating agents. The interaction between the ionophore and exogenous calcium was complex. Supramaximal concentrations of calcium potentiated the release induced by low levels of ionomycin but markedly inhibited the secretion evoked by larger amounts of the compound. Dispersed mesenteric mast cells of the rat and guinea pig also responded to ionomycin but were less reactive than the peritoneal cells.     

Canatoxin triggers histamine secretion from rat peritoneal mast cells

Canatoxin, a toxic protein present in the seeds ofCanavalia ensiformis, induces the secretion of serotonin, dopamine and insulin through activation of the lipoxygenase pathway. The purpose of the present study was to verify if canatoxin causes histamine release from rat peritoneal mast cells and to perform a detailed study of this phenomenon. Our results indicate that canatoxin is capable of activating mast cells to release histamine. The process is time- and concentration-dependent, occurs without cell damage and requires metabolic energy as well as the presence of divalent cations (Ca²⁺ and Mg²⁺). Optimal release occurs at 37°C and at physiological pH. Extremes of temperature (0°C and 45°C) inhibit the process. We conclude that canatoxin induces histamine release from rat peritoneal mast cells by an active secretory process.     

Effect of calmodulin inhibitors on histamine secretion from mast cells

Histamine secretion from isolated peritoneal mast cells was inhibited by a number of calmodulin antagonists. The characteristics of the inhibition were consistent with an action after calcium influx. The rank order of potency of the compounds correlated approximately with their reported anti-calmodulin activity. These data provide tentative support for the involvement of calmodulin in stimulus-secretion coupling in the mast cell.     

Calcium efflux and histamine secretion from rat peritoneal mast cells

Purified rat peritoneal mast cells rapidly accumulated⁴⁵calcium from the external medium. The uptake was essentially unaffected by lanthanide ions but was almost totally prevented by metabolic inhibitors. Cells preloaded with⁴⁵calcium showed a steady efflux of the cation on transfer to a medium lacking the isotope. The efflux was unaffected by metabolic inhibitors but was totally dependent on extracellular sodium ions. These results indicate the operation of a sodium-calcium exchange mechanism for the extrusion of the divalent cation. Antigenic or pharmacologic stimulation of the mast cell led to a temporary suppression of calcium efflux during the period in which histamine release occurred. This effect was potentiated by phosphatidylserine and high concentrations of the lipid inhibited basal efflux. These results suggest that activation of the mast cell leads to an inhibition of calcium extrusion, thereby potentiating the induced rise in the intracellular concentration of the cation and thus augmenting the secretory response.     

Calcium antagonists and histamine secretion from rat peritoneal mast cells

The calcium antagonists verapamil and nifedipine inhibited histamine release induced from rat peritoneal mast cells by a number of secretory stimuli. However, the concentrations required were much higher than those active in smooth muscle preparations. The inhibition was unaffected by elevated levels of external calcium and the drugs prevented release in the absence of added calcium. The novel calcium antagonist, PY 108-068, had no effect on histamine secretion from mast cells. These results suggest that calcium channels in the mastocyte may differ from those in smooth muscle and that at concentrations required to inhibit secretion, verapamil and nifedipine may have non-specific stabilizing effects on the mast cell membrane.     

Effect of ketotifen and oxatomide on histamine secretion from mast cells

The anti-histaminic drugs ketotifen and oxatomide have a dual effect on rat peritoneal mast cells. At high concentrations they induce histamine release, whereas at low concentrations they inhibit secretion evoked by IgE-directed ligands. The latter effect is observed in the presence and absence of exogenous calcium. The significance of this result for the general mode of action of anti-anaphylactic drugs is discussed. Neither compound liberates histamine from isolated mesenteric cells from the rat or guinea pig, further emphasizing the functional heterogeneity of mast cells from different sources.     

Spontaneous histamine secretion from mast cells in the presence of strontium

1. Histamine secretion from rat peritoneal mast cells occurs spontaneously in the absence of an external stimulus. Spontaneous secretion increases as the concentration of Sr in the extracellular medium is raised from 1 to 10 m-mole/l. Ca 0.1-10 m-mole/l. does not increase spontaneous secretion.2. Spontaneous histamine secretion in the presence of Sr occurs slowly compared with evoked histamine secretion, reaching a maximum only after more than 120 min incubation with Sr 10 m-mole/l. at 37 degrees C and pH 7.6. Phosphatidyl serine, 10 mug/ml., increases the rate of spontaneous secretion in the presence of Sr.3. The spontaneous secretion occurring in the presence of Sr is highly dependent on the extracellular H ion concentration. Maximal secretion occurs at pH 8.4 and only a very limited secretion is detected at pH below 7.6. The rate of spontaneous secretion is also greater at higher pH. Inhibition of secretion caused by lowering the pH can be reversed by raising the Sr ion concentration over a limited range.4. Intact glycolytic and oxidative metabolism is required for the spontaneous secretion of histamine in the presence of Sr. Removal of extracellular glucose inhibits the secretion by about 80%, and the further addition of inhibitors of oxidative phosphorylation almost abolishes the secretion.5. Ca, Mg and Mn all inhibit the spontaneous secretion of histamine which occurs in the presence of Sr. The antagonism of the effect of Sr by Mg appears not to be competitive.6. Dibutyryl cyclic AMP, 10 mumole/l. to 3 m-mole/l. and theophylline, 30 mumole/l. inhibit spontaneous secretion in the presence of Sr. Cyclic AMP, AMP, and cyclic GMP 10 m-mole/l. are without effect on the spontaneous secretion. The inhibitory effect of dibutyryl cyclic AMP and of theophylline are dependent on pH: greater inhibition being achieved at lower pH.     

Some studies on the release of histamine from mast cells treated with polymyxin

Polymyxin B produced a dose-dependent release of histamine from rat peritoneal mast cells. The response was non-cytotoxic and extremely rapid. The release was maximal in the presence of extracellular calcium ions but a substantial component persisted in the absence of the cation. This component was virtually abolished by pretreatment with the ionophore A23187 in the presence of a chelating agent and thus probably reflected the mobilization of intracellular stores of calcium. Hamster peritoneal cells also responded to polymyxin but were less reactive than those of the rat. Mouse peritoneal cells and guinea-pig lung mast cells responded only at very high concentrations. These results further emphasize the functional heterogeneity of mast cells from different sources. Histamine release from rat peritoneal mast cells was inhibited in dose-dependent fashion by cAMP analogues and anti-allergic drugs. The inhibitory effect varied inversely with the magnitude of the control secretion. With the exception of disodium cromoglycate, the test drugs were essentially equiactive in the presence and absence of extracellular calcium. These results are discussed in terms of the possible mode of action of these compounds.     

Some studies on the release of histamine from mast cells treated with d-Tubocurarine

d-Tubocurarine (dTc) released histamine in non-cytotoxic fashion from peritoneal mast cells of the rat, mouse and hamster. The response was similar to that evoked by other cationic liberators such as compound 48/80 and polylysine in that it was extremely rapid and enhanced by calcium-deprivation at suboptimal concentrations of secretagogue. Tissue mast cells obtained by enzymic dissociation of the heart, lung and mesentery of the rat and guinea pig were unreactive or hyporesponsive to the effect of dTc. The compound liberated only very small amounts of histamine from isolated preparations of perfused guinea pig heart but significantly increased the rate and contractility of the heart. These results are discussed in terms of the general functional heterogeneity of mast cells from different locations.     

Some further characteristics of histamine secretion from rat mast cells stimulated with sodium orthovanadate

Sodium orthovanadate induced a release of histamine from rat peritoneal mast cells. Other oxyanions of vanadium with the metal in the +V oxidation state also evoked histamine release but neither vanadyl sulphate (+IV oxidation state) nor the analogous orthophosphate anion were effective secretagogues. The release evoked by vanadate was selectively inhibited by the anion channel blocker SITS, and by theophylline and Bu₂cAMP, but was unaffected by disodium cromoglycate and lanthanum ions. These results are discussed in terms of the possible mode of action of vanadate.     

Inhibition of histamine secretion from mast cells by lipoxygenase- and cyclooxygenase inhibitors

We have investigated the effect of inhibitors of lipoxygenase (LOX), cyclooxygenase (COX) and dual inhibitors of both enzymes on the degranulation of peritoneal rat mast cells (pRMC) activated by different mechanisms. COX inhibitors weakly affected histamine secretion induced by A23187 and did not influence the histamine secretion induced by protamine in an isotonic medium but blocked protamine-induced release in a hypertonic medium. LOX- and dual-inhibitor inhibited secretion induced by A23187 and protamine under all conditions. As A23187 activates pRMC in an isotonic medium by Ca influx, and protamine acts in a hypertonic medium by mobilization of intracellular Ca and in an isotonic medium by both processes (this paper), LOX but not COX inhibitors, may block Ca influx, and both prevent Ca mobilization.     

On the mechanism of dextran-induced histamine secretion from rat peritoneal mast cells

The mechanism of histamine release induced from isolated rat peritoneal mast cells by clinical dextran was examined in detail. The putative involvement of cell-fixed IgE antibodies in the process was discounted by a number of experimental approaches. Instead, the characteristics of the release were found to be consistent with the interaction of the polysaccharide with specific glucoreceptors on the mast cell membrane.     

Effect of anti-allergic and cyclic AMP-active drugs on histamine secretion from rat mast cells treated with the novel calcium ionophore chlortetracycline

The anti-allergic drugs disodium cromoglycate, doxantrazole and quercetin, and a number of compounds known to elevate intracellular levels of cyclic AMP, inhibited histamine secretion from rat peritoneal mast cells stimulated with the novel calcium ionophore, chlortetracycline. The potency of the compounds varied inversely with the concentration of ionophore. The activity of the drugs cannot be explained in terms of their postulated effect on the receptor-mediated activation of calcium channels in the mast cell membrane. Alternative mechanisms for their action are thus considered.     

Kinetics of the inhibitory effect of flavonoids on histamine secretion from mast cells

The effect of cromoglycate and of natural flavonoids on histamine release from peritoneal rat mast cells induced by compound 48/80 and ionophore A23187 was studied according to preincubation time of mast cells with drugs and to incubation time of cells with the triggering agent. Preincubation of cells with cromoglycate, dihydroquercetin and amentoflavone, a biflavonoid, decreased the potency of drugs to inhibit the ionophore-induced release; the optimal inhibitions were observed when drugs were added simultaneously with the ionophore A23187. In contrast, a short preincubation (2 min) of cells with quercetin or luteolin decreased their inhibitory effect on the ionophore-induced release, whereas a longer preincubation increased the inhibition. When compound 48/80 was used to trigger histamine secretion, the inhibitory potencies of all the compounds used were decreased according to preincubation time. Dihydroquercetin (taxifolin), previously considered as inactive, showed an interesting cromoglycate-like behaviour.     

Role of cyclic AMP in the induction of histamine secretion from mast cells

Abtract Immunological activation of rat peritoneal mast cells induced a transient elevation in the intracellular concentration of cyclic AMP. Enhancement or suppression of this rise by appropriate adenosine analogues produced parallel changes in histamine secretion. However, pharmacological activation of the cell with a number of diverse ligands induced histamine release without any accompanying changes in cyclic AMP. Moreover, this release was modulated by adenosine analogues in identical fashion to IgE-directed ligands but again without affecting cyclic AMP. On the basis of these results, the possible role of cyclic AMP in the induction of histamine secretion is critically considered.     

Comparison of histamine and 5-hydroxytryptamine content and secretion in rat mast cells isolated from different anatomical locations

Rat mast cells, isolated from different anatomical locations, were found to exhibit heterogeneity with respect to histamine and 5-hydroxytryptamine (5-HT) content. Unlike peritoneal mast cells, those derived by enzymatic digestion of rat lung and mesentery tissues contained amounts of 5-HT in excess of histamine. Both compound 48/80 and A23187 were more effective liberators of histamine than 5-HT in each cell type, despite their differences in relative amine content. However, in response to a mixture of specific antigen and phosphatidylserine, the pattern of secretion of both amines from each mast cell type was observed to be essentially colinear. These results are discussed in terms of amine release mechanisms and post-secretory events.     

Role of membrane bound calcium in histamine secretion from rat peritoneal mast cells

Calcium loosely bound to the mast cell membrane may be utilized for histamine release induced by antigen, concanavalin A, compound 48/80 and the calcium ionophore A23187. Cells incubated in the presence of calcium and diluted into a medium free of divalent cations give a maximal release of histamine which decays with time, consistent with dissociation of the ion from the membrane. Anti-rat IgE and suboptimal concentrations of the ionophore show an immediate decrease in response followed by a further progressive decay. These results are consistent with the slower time-course of secretion shown by these agonists, thus permitting dissociation of calcium from the membrane before exocytosis is induced. In accord with this hypothesis, the initial supression of response to the ionophore is reversed by preincubation of the cells with adenosine which enhances the rate of histamine release. The response to dextran is totally abolished by the described treatment, supporting suggestions that free, extracellular calcium may be required for the polysaccharide to express its activity.     

A comparative study of histamine secretion from rat peritoneal and pleural mast cells

The effects of various histamine liberators and inhibitors on isolated rat peritoneal and pleural mast cells have been compared. The pleural cells showed an increased reactivity to challenge with antigen following passive, but not active, sensitization and were more responsive to challenge with anti-IgE. Phosphatidyl serine enhanced the secretion from both cell types. Peritoneal and pleural cells exhibited virtually identical responses after treatment with chemical secretagogues in the presence of exogenous calcium, but the peritoneal cells were significantly more reactive to stimulation with basic inducers in the absence of the cation. Anaphylactic histamine secretion was comparably inhibited by a number of anti-allergic drugs but the peritoneal cells were rather more sensitive to inhibition by dibutyryl cyclic AMP. These results are discussed in terms of the general functional heterogeneity of mast cells from different sources.