Synthetic peptides corresponding to the effector domain of the small molecular weight GTP-binding protein Rab3A are known to stimulate exocytosis in various secretory cells. In the present study, we report that Rab3A effector domain peptide (33-48) causes accumulation of inositol 1,4,5-trisphosphate (1,4,5-IP3) in permeabilized pancreatic acinar cells, hepatocytes, 3T3 fibroblasts, and SH-SY5Y neuroblastoma cells. A scrambled peptide of Rab3A had no effect showing specificity of the Rab3A peptide response. No effect was observed in intact cells indicating that the target of the peptide is located intracellularly. We conclude that Rab3 effector domain peptide-induced accumulation of 1,4,5-IP3 is a wide-spread phenomenon, suggesting regulation of phosphoinositide-specific phospholipase C by Rab3-like proteins.