Studies on the exocytosis of cultured mast cells derived from mouse bone marrow.

Mast cells were obtained from mouse bone marrow cells cultured for 14 days in medium derived from Concanavalin A (Con A) stimulated mouse spleen cells. Upon passive sensitization of the cultured cells with immunoglobulin E (IgE), histamine release from mast cells was approximately 200% above control within 1 min of incubation with anti-IgE. The calcium inonophore A 23187 also evoked a concentration-dependent (10(-8) M to 6 x 10(-7) M) histamine release following a 6 min incubation. Transmission electron microscopy (TEM) demonstrated that the secretory granules of the cultured cells have a peripheral crystalline pattern, like that previously demonstrated for mast cells. Scanning electron microscopy (SEM) illustrated spherical cells with surfaces traversed by many ridge-like folds. Intragranular fusion, following exposure of the IgE-bearing cells to anti-IgE, led to accumulation of the granules into channels which, on study with both transmission and scanning electron microscopy, appeared to be associated with the cell surface.