title: Calcium sensing by human medullary thyroid carcinoma cells.
abstract: Regulation of the cytoplasmic calcium concentration ([Ca2+]i) was studied in fura-2-loaded C-cells from two human medullary thyroid carcinomas (MTC). K+ depolarization induced sustained rise of [Ca2+]i reversed by verapamil. Elevation of external Ca2+ from 0.5 to 3.0 mM triggered regular oscillations or steady-state increases of [Ca2+]i. In Ca(2+)-deficient medium Sr2+ caused steady-state increase or oscillations of the 340/380 nm fluorescence ratio. The Ca2+ and Sr2+ actions were partially reversible by verapamil. La3+ and Ce3+ elicited transient [Ca2+]i peaks independent of external Ca2+, but no oscillations. The results indicate that human MTC cells express a parathyroid-like Ca2+ sensor coupled to intracellular mobilization and influx of Ca2+. A voltage-dependent Ca2+ influx may be of importance for the oscillations of [Ca2+]i.
authors.affiliation: Department of Surgery, University Hospital, Uppsala, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Ridefelt
authors.forename: Y J
authors.initials: YJ
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Rastad
authors.forename: G
authors.initials: G
authors.lastname: Akerström
authors.forename: E
authors.initials: E
authors.lastname: Gylfe
mesh_terms: D002118:Calcium / Q000378:metabolism*; D018276:Carcinoma, Medullary / Q000378:metabolism*; D002563:Cerium / Q000494:pharmacology; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002563:Cerium; D007811:Lanthanum; D014700:Verapamil; D011188:Potassium; D002118:Calcium