Bradykinin effects on phospholipid metabolism and its relation to arachidonic acid turnover in neuroblastoma x glioma hybrid cells (NG 108-15)

In neuroblastoma x glioma hybrid cells (NG 108-15) labelled with [32P]-trisodium phosphate, [3H]-inositol and [14C]-arachidonic acid, bradykinin stimulated the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) while it had no effect on the release of [14C]-arachidonic acid (AA). The effect on PIP2 was time- and dose-dependent with a maximal effect on [3H]-inositol- and [32P]-labelled cells after 10-30 s of stimulation with 10(-6) M bradykinin. However, the hydrolysis of [14C]-AA labelled PIP2 was delayed compared to the effect on [3H]- and [14C]-PIP2 and was not detectable until after 60 s of stimulation. Bradykinin stimulation resulted in an increased formation of [3H]-inositol phosphates (IP) and [32P]- and [14C]-phosphatidic acid (PA) but the time course for PA formation did not follow the time-course for PIP2 hydrolysis. A reduced labelling of [32P]- and [14C]-phosphatidylcholine was also found in stimulated cells suggesting that PA may derive from other sources than PIP2. In conclusion, our results indicate that bradykinin activates phospholipase C, but not phospholipase A2, in NG 108-15 cells.