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.