A binding site on mast cells and basophils for the anti-allergic drug cromolyn.

Calcium permeability of basophil and mast cell membranes is stimulated on allergen binding to its specific membrane-bound IgE. This entry of Ca2+ ions into the cell triggers the degranulation and secretion process. Disodium cromoglycate (cromolyn DSCG), the disodium salt of 1,3-bis(-2-carboxychromon-5-yloxy)-2-hydroxypropane, inhibits the degranulation and release of anaphylactic mediators, and has found wide application in the treatment of allergic bronchial asthma. Accumulated evidence indicates that this inhibition takes place by blocking the calcium uptake. To localize its site of action, the drug has been covalently conjugated to fluorescent polyacrylamide and polyglutaraldehyde beads (0.7 and 0.2 microns in diameter, respectively). We show here that these drug-bead conjugates (DBC) do prevent the drug penetrating into the cell without reducing its ability to inhibit histamine release (Table 1). Furthermore, we show a specific Ca2+-dependent binding of the DBC to the membranes of rat peritoneal mast cells (RPMC) and basophils.