Neurotensin Stimulates Inositol Phospholipid Metabolism and Calcium Mobilization in Murine Neuroblastoma Clone N1E‐115

Abstract Murine neuroblastoma cells (clone N1E‐115) possess neurotensin receptors that mediate cyclic GMP synthesis. Because of the hypothesized relationship between phospholipid metabolism, intracellular Ca²⁺, and cyclic GMP synthesis, we determined with these cells the effects of neurotensin on ³²P labeling of phospholipids, release of inositol phosphates, and intracellular Ca²⁺ (as determined with the use of Quin‐2, a fluorescent probe sensitive to free Ca²⁺ levels). Neurotensin stimulated incorporation of ³²P into phospholipids, especially phosphatidylinositol and phosphatidate. Neurotensin also stimulated the release of [³H]‐inositol phosphates with an EC₅₀ of about 1 nM. Mean basal Ca²⁺ concentration in these cells was 134 nM and this level was increased in a rapid and dose‐dependent manner by neurotensin, with an EC₅₀ of 4 nM. Since the EC₅₀ for neurotensin in stimulating cyclic GMP synthesis is 1.5 nM and the K_D for binding of [³H]neurotensin at 0° is 11 nM, all these different effects appear to be shared proximal consequences of neurotensin receptor activation.