Metabolic studies on the release of histamine by compound 4880 in the rat diaphragm

Inhibitory effects of carbohydrates on histamine release and mast cell disruption by dextran

Alloxan diabetic rats failed to show the skin reaction (blue spot) evoked by dextran, whereas the effects produced by histamine and compound 48/80 were not altered. When dextran and glucose were injected simultaneously into the skin the reaction was inhibited. In vitro, mast cell alterations produced by dextran occurred simultaneously with histamine release; both processes were inhibited by glucose, other carbohydrates related to glucose, and inhibitors of anaphylaxis. These experiments suggest that dextran releases histamine by a mechanism similar to that found with 48/80 and anaphylaxis in the rat. The inhibitory effect of carbohydrates may be understood on the basis of a competitive mechanism.

Compound 48/80-induced secretion of histamine from rat peritoneal mast cells depends on a tryptase controlled step also leading to chymase activity

Compound 48/80 caused activation of rat mast cell tryptase and chymase along with the release of histamine. Following low speed centrifugation, tryptase remained essentially in the supernatant while chymase sedimented. Enzyme activities as well as histamine release were inhibited by phenylmethyl-sulfonyl fluoride and tosyl-lysine chloromethyl ketone, which are respectively unspecific and specific inhibitors of trypsin-like enzymes. Chymostatin inhibited chymase, but not the release of histamine by 48/80. Tryptase activity thus seems to be essentially involved in the mechanism of histamine release, while chymase activity may be merely one of its accompanying events.

Energy metabolism in rat mast cells in relation to histamine secretion

1. The relation between the energy metabolism and the secretory activity of rat peritoneal mast cells has been studied by determination of the cellular content of ATP and the rate of lactate production reflecting the rate of ATP synthesis under various experimental conditions. Secretion of histamine was induced by the antigen-antibody reaction, the polymeric amine compound 48/80, and the divalent ionophore A23187. 2. In presence of low concentrations of metabolic inhibitors (oligomycin or antimycin A) a linear relation between the secretion of histamine induced by all three liberators and the cellular ATP content at the time of cell activation was demonstrated. This may indicate a direct link between ATP and the secretory mechanism. 3. The possibility of an increased utilization of ATP during histamine secretion was explored in mast cells exposed to metabolic inhibitors. Incubation of mast cells with 2-deoxyglucose (2-DG) decreased the ATP content of the cells, and a long-lasting and stable level of mast cell ATP was observed. This is explained by a small decrease in the rate of ATP-synthesis by 2-DG. In 2-DG-treated cells secretion of histamine in response to compound 48/80 or the antigen-antibody reaction could still occur, and the secretion is shown to be associated with a decrease of the cellular ATP level. This ATP decrease indicates that secretion occurs by an ATP-requiring mechanism, that causes an increased cellular utilization of ATP in association with the secretory response. 4. The possibility has been considered that increased cytosol concentration of calcium in association with secretion may decrease the rate of ATP-synthesis due to accumulation of calcium by the mitochondria. This possibility can be excluded by the observation that in presence of respiratory inhibitors an identical ATP decrease was found during the secretion as in the case of the glycolytic inhibitor alone. This indicates that increased utilization of ATP by the cells was related directly to the secretory response. This observation was made with all three secretagogues. 5. A quantitative evaluation of the increased amount of ATP utilized by the cells in relation to the secretory response was performed by use of metabolic inhibitors. The ATP requirement of compound 48/80-induced secretion was 0.15 pmol/10(3) cells. This was observed when the ATP-synthesis was decreased to a negligible value.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of plasma membrane Ca++-Mg++ activated adenosine triphosphatase of rat mast cells on histamine release

The role of a Ca++-MG++ activated ATPase, demonstrated on the outer surface of rat peritoneal mast cells, on histamine release induced by antigen (anaphylactic reaction), compound 48/80 and ionophore A23187 has been studied. A high level of the enzyme activity is retained at the optimal pH for histamine release induced by the three releasing agents. The effect of fourteen inhibitors of ATPase has been studied, viz. quinidine, fluoride, platinum salt, suramin, ethacrynic acid, ethyl alcohol, N-ethylmaleimide, Mn++, Ni++, ADP, AMP and the flavones: kaempferol, quercetin, morin. All the inhibitors, which caused varying degrees of inhibition of ATPase, also inhibited histamine release. The inhibition of the enzyme was competitive with ADP, AMP, ethacrynic acid, suramin and morin and non-competitive with the others. The degree of inhibition of ATPase and of histamine release tended to be similar with six inhibitors. With the others the extent of the inhibition of the release and of the enzyme varied. But a marked inhibition of the enzyme was always associated with a pronounced inhibition of histamine release. ATP in lower concentrations (10-20 microM) has been shown to potentiate histamine release induced by all the three releasers, possibly through its utilization by plasma membrane ATPase. The observations agree with the hypothesis that plasma membrane ATPase participates in the histamine release process.

Mechanisms of histamine release by compound 48-80

1. Rat and guinea-pig lung tissues were incubated for 20 min at 37 degrees C in Krebs-Ringer phosphate buffer at pH 7.4, or in Tyrode-Tris buffer at pH 8.2, and the release of histamine produced by adding different concentrations of compound 48/80 to the incubation medium was determined.2. At pH 7.4, increasing concentrations of 48/80 increased the release of histamine from the rat lung, with a tendency towards a maximum. No release of histamine from guinea-pig lung was observed at this pH. At pH 8.2, histamine release occurred both from rat and guinea-pig lung, and was proportional to the logarithm of the concentration of compound 48/80.3. Histamine release from rat lung by 20 mug/ml. of 48/80 decreased when the pH was raised from 7.4 to 8.2; but the release caused by 1 mg/ml. of 48/80 increased both in rat and guinea-pig lung as the pH was raised.4. 2-4-Dinitrophenol (DNP) inhibited the release of histamine from rat lung by a concentration of 20 mug/ml. of 48/80; the inhibition was prevented by glucose. DNP did not affect histamine release from rat or guinea-pig lung by a concentration of 1 mg/ml. of 48/80 and enhanced the release when the pH was raised from 7.4 to 8.2.5. 1 mg/ml. of 48/80 did not inhibit the enhanced oxygen consumption produced by DNP in the isolated rat diaphragm.6. Iodoacetic acid (IAA) or a Ca/Mg-free medium inhibited the release of histamine by 20 mug/ml. of 48/80 from rat lung but not the release produced by 1 mg/ml. in either rat or guinea-pig lung.7. The degranulation of rat mesentery mast cells caused by 20 mug/ml. of compound 48/80 was inhibited by DNP. The degranulation evoked by 1 mg/ml. of 48/80 was also sensitive to this inhibitor; in this instance, however, the metachromatic staining reaction of the mesentery mast cells was greatly diminished.8. It is concluded that two processes of histamine release by compound 48/80 occur in rat lung. One, dependent on cell metabolism, involves, mast cell granule secretion. The other, independent of cell metabolism, seems to consist of a simple exchange reaction between histamine and compound 48/80, and this is the only one occurring in guinea-pig lung.