Investigation of rat mast cell degranulation using flow cytometry

Mast cells degranulation has been assessed by flow cytometry (FACS) taking advantage of the changes in the light scattering properties of mast cells stimulated by secretagogues. In turn, these changes are based on the modification of size, shape, and granule content of the cells before and after stimulation. With FACS, it is possible to work with almost pure mast cell populations (greater than 99%). Moreover, responses to compound 48/80 are carried out in real time and on the same cell sample that acts as internal control. This technique is very sensitive as shown by the ED50 of compound 48/80 (0.051 micrograms/mL) compared to its ED50 on histamine release (0.131 micrograms/mL). The well-known inhibitory effect of disodium cromoglycate against compound 48/80 was clearly observed using FACS. Furthermore, FACS allowed to distinguish between specific degranulating effects and cytotoxicity. Among the secretagogues used, only the degranulation induced by phospholipase A2 was inhibited by in vivo treatment with dexamethasone. It is suggested that the inhibitory effect is due to induction of phospholipase A2-inhibitory proteins (lipocortins).