Degranulation of mast cells is stimulated by store-operated Ca2+-entry (SOCE). In other cell types, Ca2+-entry is modified by ceramide. Exogenously added ceramide has been shown to trigger mast cell apoptosis. Effects of endogenously produced ceramide in mast cells remained, however, elusive. Ceramide may be produced from sphingomyelin by acid sphingomyelinase (Asm).