Stimulation of Inositol Incorporation into Lipids of PC 12 Cells by Nerve Growth Factor and Bradykinin

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Abstract
The effects of bradykinin (BK) and lithium on the phosphatidylinositol cycle were examined in PC 12 cells cultured for 20 h in the presence [PC12 (+)] or in the absence [PC12 (−)] of nerve growth factor (NGF). BK (1 nM) induced a small stimulation of the incorporation of m′o‐[2–3H] inositol into the lipids of PC12 (−) ceils and a three‐ to fourfold stimulation of such incorporation into the lipids of PC12 (+) cells. About 15 h of incubation with NGF and >10 min of incubation with BK were needed for maximal stimulation of inositol incorporation by BK. In the presence of 25 mM LiCl, BK stimulated the inositol monophosphate levels ninefold in PC12 (−) and 30‐fold in PC12 (+) cells. After incubation for 20 h with NGF, an increased binding of [3H]BK to the PC12 (+) cells was observed at 4°C. Exposure of the cells for 30 min to 25 mM LiCl enhanced the effect of BK on the inositol incorporation into total inositol lipids, especially in PC 12 (+) cells. In these cells, LiCl in the presence of BK also increased several‐fold the intracellular levels of inositol bisphosphate and inositol trisphosphate.