Localized mast cell degranulation induced by concanavalin A-sepharose beads. Implications for the Ca2+ hypothesis of stimulus-secretion coupling.
Concanavalin A (Con A) covalently linked to Sepharose 4B beads induced localized degranulation of sensitized rat peritoneal mast cells in regions of contact between beads and cells. This degranulation was Ca2+ dependent and was not seen when sensitized mast cells bound to beads conjugated with a nonstimulating lectin, wheat germ agglutinin, or when unsensitized mast cells bound to Con A-Sepharose. The finding that sensitized mast cells which had adhered to Con A-Sepharose beads degranulated in regions of the cell away from the area of bead contact if exposed to soluble Con A excluded the possibility that the localized release was due to a redistribution of the IgE receptors or putative Ca2+ channels to the region of bead contact. The results suggest that, if an influx of Ca2+ is the mechanism for initiating mast cell degranulation, then the opening of Ca2+ channels in the plasma membrane of activated mast cells is a localized event and that Ca2+ acts locally within the cell to initiate exocytosis.
D000818:Animals; D001666:Binding Sites, Antibody; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D003208:Concanavalin A / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000502:physiology*; D005089:Exocytosis; D007073:Immunoglobulin E; D037102:Lectins / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats
D037102:Lectins; D003208:Concanavalin A; D007073:Immunoglobulin E; D002118:Calcium