Changes in polyphosphoinositide metabolism during mediator release from stimulated rat mast cells

The metabolism of the polyphosphoinositides, diphosphoinositide (DPI) and triphosphoinositide (TPI), was studied during mediator release from rat mast cells. Serosal mast cells were purified by density gradient centrifugation and prelabeled with 32PO4. Incorporation of 32PO4 into DPI and TPI was determined by thin-layer chromatography on oxalic acid impregnated silica gel plates. 32PO4 incorporation into DPI and TPI was increased by Concanavalin A (ConA) or compound 48/80. The concentration of ConA causing a half-maximal increase in DPI labeling was less than that required for a comparable change in histamine release. The increases in DPI labeling and histamine release in response to ConA were enhanced by phosphatidylserine. The addition of alpha-methylmannoside to mast cells after challenge with ConA rapidly halted DPI and TPI labeling. The results of these studies indicate that changes in the metabolism of polyphosphoinositides may be an intrinsic part of the biochemical mechanisms that control mediator release from mast cells.