INHIBITION BY CROMOGLYCATE OF HISTAMINE RELEASE FROM RAT PERITONEAL MAST CELLS INDUCED BY MIXTURES OF DEXTRAN, PHOSPHATIDYL SERINE AND CALCIUM IONS

Abstract

1 Dextran releases histamine from rat peritoneal mast cells in the presence but not in the absence of phosphatidyl serine (PS). With PS (10 μg/ml) present the effect of dextran was concentration-dependent in the range of 0.2–6 mg/ml. 2 PS releases little histamine on its own but mixed with dextran (6 mg/ml) produces a graded effect in the range of 0.3–10 μg/ml. 3 The combination of dextran and PS releases no histamine in a medium containing less than 0.1 mm calcium. As the calcium concentration is increased, release occurs and a maximum is reached at calcium 1 mm; at higher concentrations release falls off sharply. 4 Histamine release by the combination of dextran (6 mg/ml), PS (10 μg/ml) and calcium (1.8 mm) is inhibited by cromoglycate in the same range (1–30 μm) that inhibits anaphylactic histamine release from rat peritoneal cells. 5 Inhibition by cromoglycate occurred with all dextran concentrations tested (0.2–15 mg/ml) but high concentrations of PS (30 and 100 μg/ml) overcame the effect of cromoglycate (2 and 10 μm). Calcium concentrations above 1 mm augmented inhibition by cromoglycate 2 and 10 μm.