Bradykinin-induced generation of inositol 1,4,5-trisphosphate in fibroblasts and neuroblastoma cells: Effect of pertussis toxin, extracellular calcium, and down-regulation of protein kinase C

The net content of inositol 1,4,5-trisphosphate [Ins(1,4,5)P₃] was measured in bradykinin (BK)-stimulated NIH3T3 fibroblasts and neuroblastomaglioma hybrid cells (NG108-15). BK-mediated production of Ins(1,4,5)P₃ was not affected by replacing the medium with Ca²⁺-free medium, but addition of EGTA(1mM) to Ca²⁺-free medium markedly prevented production of Ins(1,4,5)P₃. Although perussis toxin (PT) treatment caused ADP-ribosylation in both N1H3T3 cells and NG108-15 cells, the BK-induced Ins(1,4,5)P₃ formation was considerably reduced in the former cells but not in the latter cells, suggesting that PT-sensitive and PT-insensitive GTP-binding proteins are involved in phosphoinositide phospholipase C (PI-PLC) activation in fibroblasts and neuroblastoma cells, respectively. In NG108-15 cells down-regulated in protein kinase C (PKC) by long-term exposure to phorbol 12-myristate 13-acetate (PMA), BK-stimulated Ins(1,4,5)P₃ accumulation was significantly enhanced compared to control cells.