Stimulation of inositol phosphate production and GTPase activity by compound 48/80 in rat peritoneal mast cells.

Phospholipase C activity, GTPase activity and cytosolic-free calcium concentration in mast cells were stimulated by compound 48/80. Accumulation of inositol phosphates in rat mast cells was stimulated by guanosine 5'-[gamma-thio]-triphosphate. Guanosine 5'-[gamma-thio]triphosphate, however, exhibited no effect upon the purified phospholipase C activity and upon phospholipase C in the mast cell homogenate. The stimulatory effect of compound 48/80 upon phospholipase C activity of intact mast cells was observed to have been well correlated with that on GTPase activity of mast cell homogenate. Compound 48/80 exhibited no effect upon the binding of radioactive guanosine 5'-[gamma-thio]triphosphate to mast cell homogenate. Phospholipase C activity was verified by the above results to become affected by compound 48/80 through guanine nucleotide-binding regulatory protein.