HISTAMINE-RELEASE INDUCED BY HISTONE AND RELATED MORPHOLOGICAL-CHANGES IN MAST-CELLS

When isolated rat peritoneal mast cells were exposed to histone mixture, both histamine release and degranulation were evoked rapidly and dose-dependently at concentrations higher than 1 μg/ml in a Ca-free medium. All of the histone subfractions (H1, H2A, H2B, H3 and H4) induced histamine release from mast cells in a Ca-free medium and, as in the case of histone mixture, the amount of histamine release was reduced by addition of Ca2+. By means of high-voltage electron microscopy, at least three types of degranulation were observed in mast cells exposed to histone mixture: (1) microfilament-associated degranulation, (2) extrusion of granules with the surrounding membrane, and (3) mass degranulation. © 1990 Birkhäuser Verlag.