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A slowly inactivating calcium current works as a calcium sensor in calcitonin‐secreting cells
Author(s) -
Scherubl H.,
Schultz G.,
Hescheler J.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81048-s
Subject(s) - extracellular , chemistry , calcium , biophysics , calcitonin , depolarization , patch clamp , membrane potential , current clamp , voltage clamp , endocrinology , medicine , microbiology and biotechnology , biochemistry , biology , receptor , organic chemistry
Calcitonin (CT)‐secreting cells (C‐cells) are remarkably sensitive to changes in the extracellular Ca 2+ concentration. In order to detect the mechanism by which C‐cells monitor Ca 2+ , we compared a C‐cell line responding to Ca 2+ (rMTC cells) with another one known to have a defect in this Ca 2+ signal transduction (TT cells). Rises of the Ca 2+ concentration caused rMTC cells to depolarize and/or elicited spontaneous action potentials. Under voltage‐clamp conditions, rMTC cells showed a slowly decaying Ca 2+ inward current which was sensitive to dihydropyridines but not to Ni 2+ at a low concentration. In contrast, the ‘defective’ TT cells neither depolarized nor fired action potentials with high Ca 2+ ; they only exhibited an Ni 2+ ‐sensitive, transient Ca 2+ current. The data strongly suggest that the slowly inactivating Ca 2+ current is a prerequisite for Ca 2+ ‐sensitivity of C‐cells and that fast inactivating channels are not sufficient to act as sensors of the extracellular Ca 2+ concentration.