Histamine release induced by dextran: the nature of the dextran receptor

Dextrans of molecular weight 10(4) to 2 x 10(6) induced histamine release from rat peritoneal mast cells in the presence of calcium (1 mM) and phosphatidyl serine (10 micrograms/ml). Glucose and low molecular weight dextrans inhibited the histamine release induced by high molecular weight dextrans but the inhibition could not be explained in terms of a simple competitive model. Structure-activity relationships for the inhibition of dextran-induced histamine release by a number of saccharides demonstrated that substitution at the C-3, C-4, and C-6 positions of glucose were most important for activity. Inhibition of histamine release by glucose was specific for the dextran stimulus. Soluble IgE and IgG antibodies failed to interfere with histamine release induced by dextran. Phlorizin specifically inhibited the histamine release induced by dextran. Purification of mast cells on albumin or ficoll gradients produced a selective loss of response to dextran which was not due to the removal of non-mast cells but to some change in the mast cells themselves. The possible nature of the dextran receptor is discussed.