Madeleine Ennis

THE EFFECT OF ALKALINE EARTH CATIONS ON THE RELEASE OF HISTAMINE FROM RAT PERITONEAL MAST CELLS TREATED WITH COMPOUND 48/80 AND PEPTIDE 401

1 Extracellular calcium ions have a dual effect on the release of histamine from rat peritoneal mast cells treated with compound 48/80 and peptide 401. The release is either potentiated or inhibited according to the relative concentrations of ion and inducer. 2 Strontium similarly potentiates the release produced by optimal concentrations of inducer but higher concentrations are required than in the case of calcium. Strontium is markedly less inhibitory than calcium. 3 Mast cells may be depleted of intracellular calcium by incubation for short periods with the chelating agent, ethylenediamine tetraacetic acid (EDTA). They thereby become unresponsive to compound 48/80 and peptide 401 unless calcium is reintroduced into the incubation medium. Strontium and barium, but not magnesium, will substitute for calcium in this system. Barium additionally produces a marked release of histamine even in the absence of inducer. Pretreatment with the ionophore A23187 similarly inhibits the subsequent response to peptide 401 in divalent cation‐free medium. This inhibition is reversed on the reintroduction of calcium. 4 Compound 48/80 and peptide 401 release histamine from mast cells incubated in isotonic sucrose in the complete absence of added metal ions. However, the corrected release under these conditions is potentiated by both mono and divalent cations. 5 On the basis of these results, the possible mechanism of action of the basic releasing agents and their usefulness as models for studying histamine secretion is discussed.

Role of intra- and extracellular calcium in histamine release from rat peritoneal mast cells

The present study provides evidence for a number of calcium pools important in histamine secretion from the mast cell. Firstly, calcium loosely bound to the cell membrane, and in rapid equilibrium with the extracellular environment, may be utilized for histamine release induced by most secretagogues. Secondly, all inducers are able to mobilize deeply buried or internal stores of calcium to initiate exocytosis. Finally, calcium bound to regulatory sites in the membrane may modulate the secretory process. Removal of calcium from the latter sites by brief treatment with chelating agents markedly enhances the secretory response in the absence of extracellular calcium, probably by facilitating the mobilization of bound stores of the ion. Saturation of these sites in the presence of excess calcium inhibits the release process and may restrict influx of the cation.

Calcium Pools Involved in Histamine Release from Rat Mast Cells

Basic secretagogues, antigen, concanavalin A, the ionophore A23187 and, to a lesser extent, anti-rat IgE produce a significant release of histamine from rat peritoneal mast cells in the absence of extracellular calcium. This release is due to the mobilization of intracellular reservoirs of calcium. The release is abolished by prolonged exposure to chelating agents, but is potentiated by brief exposure to these substances. It is suggested that the latter treatment removes calcium from a superficial, regulatory site and thus facilitates the mobilization of more internal pools of the ion. By analogy with smooth muscle, these regulatory sites may also modulate calcium influx into the cell. On the basis of these and other results, the possible calcium pools important in histamine secretion are discussed.

ISOLATION AND SOME PROPERTIES OF MAST-CELLS FROM THE MESENTERY OF THE RAT AND GUINEA-PIG

A number of enzymes were screened for their ability to dissociate mesenteric tissues from the rat and guinea pig into their component cells. The bacterial enzyme collagenase was found to be the most satisfactory agent and a procedure based on the use of this protease was developed. The resulting suspensions contained 1–2% free mast cells and exhibited a low (ca. 5%) spontaneous release of histamine. The tissue cells contained less histamine than rat peritoneal mast cells and the guinea pig cells were smaller in size. Cells obtained from actively sensitized animals responded to antigenic challenge more strongly than the chopped tissue indicating that they were functionally intact. Rat mesenteric cells could be passively sensitized with homologous reaginic antibody and also responded to anti-rat IgE. The immunologically induced releases from rat mesenteric and peritoneal cells showed differing sensitivities to potentiation by phosphatidyl serine but the responses were directly comparable in the absence of this effect. Rat mesenteric cells also responded, but less effectively than the peritoneal cells, to the ionophore A23187, concanavalin A, ATP and basic secretagogues. They were, however, essentially refractory to the action of dextran. In contrast, guinea pig mast cells responded strongly only to the ionophore and weakly or not at all to the other agents. These results indicate marked inter-and intra-species differences in the reactivity of mast cells and suggest that rat peritoneal cells should not be used as the sole model for studying histamine secretion.

Differential reactivity of isolated mast cells from the rat and guinea pig

The effects of various chemical histamine liberators on isolated rat peritoneal, rat mesenteric and guinea-pig mesenteric mast cells were examined. All three cell types responded, but to different degrees, to calcium ionophores and surface active agents. The rat mesenteric cells also reponded, but less effectively than the peritoneal cells, to compound 48/80, peptide 401 from bee venom and ATP. Rat mesenteric cells were essentially refractory to the action of dextran and guinea-pig cells were almost totally unresponsive to the named secretagogues. These results show that there are marked functional differences between the mast cells examined and suggest that isolated tissue cells may usefuly complement rat peritoneal cells in the study of anaphylactic and anaphylactoid reactions.

HISTAMINE-RELEASE INDUCED BY RADIOGRAPHIC CONTRAST-MEDIA - COMPARISON BETWEEN PULMONARY AND PERITONEAL MAST-CELLS DERIVED FROM NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS

Intravascular application of radiographic contrast media (RCM) can cause adverse allergic/pseudoallergic reactions in certain individuals. In view of the increased risk for the reactions associated with cardiovascular diseases, we have investigated histamine release from isolated mast cells derived from the peritoneal cavity and the lung of normotensive and spontaneously hypertensive rats. Six commonly used RCM were tested in their clinical formulations: Angiographin (amidotrizoate), Rayvist (ioglycate), Telebrix (ioxithalamate), Hexabrix (ioxaglate), Solutrast (iopamidol), and Ultravist (iopromide). The three RCM with low osmolality (Hexabrix, Solutrast and Ultravist) released little histamine from all cell populations tested. Mast cells derived from spontaneously hypertensive rats released significantly more histamine following challenge with high osmolar RCM than those derived from normotensive rats. Higher concentrations were required to elicit release from the peritoneal cells than from the pulmonary cells. These results indicate a role for underlying cardiovascular diseases in mediator release and should be followed up by investigations on basophils or mast cells obtained from control subjects and patients with cardiovascular disease.

Some studies on the mechanism of action of antibodies to nerve growth factor

Abstract The effects of antibodies to the nerve growth factor from mouse salivary gland were examined in vitro and in vivo. Treatment of explants of receptive ganglia with antibody and complement did not produce cell damage as judged by the ability of the tissue to respond to nerve growth factor. New-born mice experimentally depleted of or genetically deficient in key complement components were susceptible to the action of the antiserum. These results show that the effect of the antibody is independent of complement and are consistent with the view that it acts by neutralization of endogenous nerve growth factor.

Action of 3-Isobutyl-1-Methylxanthine and Prostaglandins D2 and E1 on Histamine Release from Rat and Guinea Pig Mast Cells

The action of three compounds reported to elevate intracellular cyclic adenosine monophosphate (cAMP) namely 3-isobutyl-1-methylxanthine (IBMX) and prostaglandins D2 and E1 (PGD2 and PGE1), on histamine release was examined. Three test systems were used: (i) the perfused ovalbumin-sensitized guinea pig lung and (ii) isolated cells from ovalbumin-sensitized guinea pig lung, both of which are IgG-mediated models of anaphylaxis, and (iii) an IgE model of anaphylaxis, using isolated rat peritoneal mast cells from sensitized rats. Both PGD2 and PGE1 were without effect at concentrations likely to be found during anaphylaxis. In contrast, the phosphodiesterase inhibitor, IBMX, was highly active in all three test systems. The role of raised intracellular cAMP levels in the inhibition of histamine release is discussed.

Effect of in vivo and in vitro lovastatin treatment on mast cell activation

The hydroxymethylglutaryl coenzyme A (HMG CoA) reductase inhibitor lovastatin is used to treat hyperlipidaemia. This agent prevents the isoprenylation of some proteins involved in signal transduction processes and inhibits IgE-receptor-linked mediator release from RBL-2H3 cells. In this study the effect of in vivo and in vitro administration of lovastatin on histamine release from rat peritoneal mast cells was examined. Lovastatin (4 mg/kg/day for 2 weeks) inhibited histamine release induced by concanavalin A (con A) from rat peritoneal mast cells of Hooded-Lister rats and both homozygous lean and obese Zucker rats. In contrast, release induced by antirat IgE (anti-IgE) was only significantly inhibited in cells derived from Hooded-Lister rats and that induced by compound 48/80 was not altered. Lovastatin (20 microM, 24 h, in vitro) caused a significant inhibition of the subsequent histamine release to con A, anti-IgE and compound 48/80 but not to the calcium ionophore A 23187. It is important to determine whether such inhibitory effects are also observed after the chronic, clinical administration of lovastatin and other HMG CoA reductase inhibitors.

Studies on histamine release induced by compound 48/80 and peptide 401

ConclusionThe activity of the drugs under these conditions suggests that they, and possibly cyclic AMP, may have a wider role in regulating the intracellular concentration of calcium, whether derived from internal or external sources, or that they may have activities unrelated to calcium movements.