Regulation of neurotensin secretion in a mammalian C cell line: effect of dexamethasone.
We established in culture two colony clones of rMTC 44-2 cells, rMTC 44-2B and 44-2C which secrete substantially greater quantities of neurotensin (NT) than the parent cell line. We describe here the effects of the synthetic glucocorticoid, dexamethasone, on NT and cAMP release. Medium and intracellular levels of NT and cAMP were measured by specific RIAs. Long-term release experiments were performed in Dulbecco's Modified Eagle's Medium supplemented with 15% horse serum (DMEM). Short-term release experiments were performed in Krebs-Ringer-bicarbonate-glucose buffer (KRBG) supplemented with 1.0 mm Ca2+. Dexamethasone stimulated NT release and increased intracellular NT levels. The ED50 values for stimulation of NT release following 24 or 48 h incubation of cells in DMEM with dexamethasone were 5 X 10(-9) and 7 X 10(-9) M, respectively. Dexamethasone markedly enhanced intracellular levels of NT in rMTC 44-2 cells while it decreased cell growth. Cells pretreated with dexamethasone for 48 h released greater amounts of NT in response to Ca2+ (1.0 mM) with or without K+ (50 mM) or NE (10(-6) M) following a 10 min incubation with these substances in KRBG. This experimental paradigm was also used to measure the efflux of cAMP following a brief (10 min) exposure of cells to NE. We conclude that the rMTC 44-2B and 44-2C cells are useful tools for studying the effects of dexamethasone on the regulation of cell growth, as well as the secretion of NT and cAMP.
D000818:Animals; D002116:Calcitonin / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002999:Clone Cells; D003907:Dexamethasone / Q000494:pharmacology*; D007700:Kinetics; D009374:Neoplasms, Experimental / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D013964:Thyroid Neoplasms / Q000378:metabolism*
D009496:Neurotensin; D003907:Dexamethasone; D002116:Calcitonin; D002118:Calcium; D009638:Norepinephrine