Time Course of Anaphylactic Histamine Release and Morphological Changes in Rat Peritoneal Mast Cells

Anaphylactic histamine release and concomitant morphological changes were studied in rat peritoneal mast cells. It was found that anaphylactic histamine release has a longer lag period than compound 48/80‐induced release. The time sequence of the morphological changes showed a close correlation to the histamine release. These changes were essentially characterized by vacuolation, granule alteration and granule extrusion. Some peripheral granules were extruded with only minor changes. The ultrastructural findings are consistent with a dual mechanism of histamine release—both intracellular and extracellular following granule extrusion.