Presence of SNAP-25 in rat mast cells.

Mast cells participate in inflammation and allergies by releasing active mediators stored in numerous cytoplasmic granules. Degranulation implies compound exocytosis which involves a combination of granule-granule and granule-plasma membrane fusions. One of the most important proteins in the exocytotic process in neural and endocrine cells is the synaptosomal associated protein of 25 kDa (SNAP-25). In the present study, using a highly specific monoclonal antibody against SNAP-25, we have demonstrated by immunocytochemistry, western blot and immunoelectron microscopy the presence of SNAP-25 in rat peritoneal mast cells. Likewise we localized the protein mainly on the membrane of the secretory granules. Thus while the precise function of SNAP-25 in mast cells remains to be elucidated, it may be envolved in granule-granule fusion needed in degranulation.