Regulation of Neurotensin Release by a Continuous Line of Mammalian C-Cells: The Role of Biogenic Amines*

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Abstract
We describe here the establishment of a new cell line [rat medullary thyroid carcinoma (rMTC) 44–2] derived from a transplantable WAG/Rij rMTC which produces substantially greater quantities of neurotensin (NT) than calcitonin. The rMTC 44–2 cell line was used to investigate the regulation of NT secretion by biogenic amines. Medium and intracellular levels of NT and calcitonin were measured by specific RIAs. Release experiments (1 h or less) were performed in Krebs- Ringer bicarbonate-glucose buffer supplemented with 1.0 mM Ca++. Several biogenic amines stimulated NT release with relative activities: epinephrine (E) > norepinephrine (NE) > isoproterenol > histamine > dopamine > 5-hydroxytryptamine. LTryptophan and L-dopa did not stimulate NT release. The ED50 values for stimulation of NT release by E and NE were about 108 and 10-7 M, respectively; a maximal effect occurred at 10-6 M for both E and NE. NE-stimulated NT rel se was detected in less than 1 min and reached a maximum at 20–30 min. NEstimulated NT release was inhibited by the β-adrenergic antagonist propranolol. Extracellular calcium was required for basal and NE-stimulated NT release. Ca++-dependent release of NT was also shown with depolarizing concentrations of K+. After repetitive stimulation of cells by NE, partial loss of response to the amine was observed. We conclude that the rMTC 44–2 cell line provides a model for studying the regulation of NT secretion by catecholamines.