ULTRASTRUCTURAL-STUDY OF MAST-CELLS STIMULATED WITH COMPOUND-48 80 ASREVEALED BY QUICK-FREEZING METHOD/

The ultrastructure of mast cells stimulated with compound 48/80 was ex amined by quick-freezing and deep-etching (QF-DE) or freeze-substituti on (QF-FS) methods. Peritoneal cells including mast cells of adult mal e rats were stimulated in vitro with compound 48/80 at 17 degrees C fo r 0, 10, 30, 60 or 180 s. The QF-DE replicas revealed that the mast ce lls stimulated with compound 48/80 for 30 s decreased filamentous acti n around secretory granules. In the QF-FS specimens, perigranular memb ranes in mast cells stimulated for 60 s formed pentalaminar structures between adjacent granules in their cytoplasm prior to degranulation. These findings suggest that preparatory states for degranulation occur in the whole cytoplasm of stimulated mast cells at early stages. More over, both QF-FS specimens and QF-DE replicas revealed a compact morph ological appearance of discharged granules in the extracellular space, indicating the existence of considerable content within the granules. Skeletal structures in the granules were also demonstrated on QF-DE r eplicas prepared after extracting soluble elements from the cytoplasm. It is suggested that the granular contents associated with the skelet al structures are gradually detached from the discharged granules to e nsure local concentration in the tissues.