Abstract
1. Unstimulated mast cells from the peritoneal cavity of the rat take up (45)Ca: the initial phase of rapid uptake being 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 (45)Ca which is accompanied by a release of granular material: this increase in (45)Ca uptake is also complete in 1 min. The majority of the stimulated (45)Ca 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.2. The magnitude of the increase in (45)Ca uptake caused by stimulating the mast cells increases when the degree of histamine secretion increases.3. The increased (45)Ca 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 (45)Ca uptake and secretion with maxima at pH 7.5.4. Two thirds of the (45)Ca uptake induced by an antigen-antibody reaction or by the Ca ionophore A 23187 is unaffected by inhibiting glycolysis and oxidative phosphorylation. Histamine secretion on the other hand is practically abolished by this metabolic inhibition. Thus, (45)Ca uptake proceeds in the absence of the discharge of granules.5. Dibutyryl cyclic AMP or theophylline inhibit both the increase in (45)Ca uptake and the histamine secretion caused by stimulating mast cells with an antigen-antibody reaction. Cyclic AMP, cyclic GMP and dibutyryl cyclic GMP have no effect on uptake or secretion.6. The Ca ionophore, A 23187, induces uptake of (45)Ca and histamine secretion, neither effect being inhibited by either dibutyryl cyclic AMP or theophylline.7. Phosphatidyl serine increases both (45)Ca uptake and the histamine release induced by an antigen-antibody reaction, dextran or concanavalin A.
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