ELECTRON MICROSCOPE OBSERVATIONS ON COMPOUND 48/80-INDUCED DEGRANULATION IN RAT MAST CELLS: Evidence for Sequential Exocytosis of Storage Granules

摘要: In vitro degranulation of rat mast cells was studied at different intervals ranging from 10 to 60 sec after adding the histamine liberator, compound 48/80 (0.4 µg/ml, 17°C). The ultrastructural changes were followed by electron microscopy, and parallel assays made determine released. addition, extracellular tracers lanthanum hemoglobin (demonstrated its peroxidative activity) applied follow communication space with cavities formed during degranulation. After a lag period sec, started in most peripherally located granules. perigranular membrane fused plasma membrane, resulting pore bridged thin diaphragm. This rupture diaphragm extrusion granule matrix (exocytosis). process advanced towards cell interior fusion opening deeper situated granules formerly opened cavities. At end process, filled system complicated containing number altered Extracellular have shown that these intracellular unbroken very beginning their formation. Both found be adsorbed limiting bound contrast, no tracer substance present nondegranulating cells. Degranulation is regarded as sequential exocytosis, similar described for some exocrine gland All "intracellular" cavities, degranulation, communicate space; consequently, lying must considered biologically extracellular. findings support view released ionic milieu.