The relationship between histamine secretion and 45calcium‐uptake by mast cells

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Abstract
Unstimulated mast cells from the peritoneal cavity of the rat take up 45Ca: the initial phase of rapid uptake is complete after 1 min incubation of the cells with the isotope. Stimulation of the mast cells with an antigen-antibody reaction, dextran or concanavalin A induces an increase in the uptake of 45Ca which is accompanied by a release of granular material: this increase in 45Ca uptake is also complete in 1 min. The majority of the stimulated 45Ca uptake cannot be explained in terms of binding of Ca to released granular material, or to an enlargement in either the extracellular compartment or the cell surface area. The magnitude of the increase in 45Ca uptake caused by stimulating the mast cells increases when the degree of histamine secretion increases. The increased 45Ca uptake induced by stimulation of the mast cells and the degree of histamine secretion are both dependent on extracellular H ion concentration. Changes of pH cause similar changes in 45Ca uptake and secretion with maxima at pH 7.5. Two thirds of the 45Ca uptake induced by an antigen-antibody reaction or by the Ca ionophore A 23187 is unaffected by inhibiting glycolysis and oxidative phosphorylation. Histamine secretion is practically abolished by this metabolic inhibition. 45Ca uptake usually proceeds in the absence of the discharge of granules. Dibutyryl cyclic[c]AMP or theophylline inhibit both the increase in 45Ca uptake and the histamine secretion caused by stimulating mast cells with an antigen-antibody reaction. cAMP, cGMP and dibutyryl cGMP have no effect on uptake or secretion. The Ca ionophore, A 23187, induces uptake of 45Ca and histamine secretion, neither effect being inhibited by either dibutyryl cAMP or theophylline. Phosphatidyl serine increases both 45Ca uptake and the histamine release induced by an antigen-antibody reaction, dextran or concanavalin A.