Extracellular Ca2+ Sensing in C-Cells and Parathyroid Cells

Authors

Hans Scherubl
Maria Luisa Brandi
Jurgen Hescheler

Abstract

An essential function of C-cells and parathyroid cells is to monitor the extracellular Ca²⁺ concentration. The Ca²⁺-dependent secretion of calcitonin (CT) and parathyroid hormone is known to be mediated by corresponding changes in the intracellular Ca²⁺ concentration. To address the question of whether Ca²⁺ influx through voltage-dependent Ca²⁺ channels couples the extracellular to the intracellular Ca²⁺, we applied the patch clamp technique to C-cells of the rMTC 44-2 cell line and to parathyroid cells of the PT-r cell line. The rMTC cells displayed dihydropyridine-sensitive, voltage-dependent, high-threshold Ca²⁺ channels which allowed ion influx even at the resting potential of about -40 mV. Increases of the concentration of the extracellular divalent cation or adding the Ca²⁺ channel agonist Bay K 8644 stimulated the steady state ion influx. In contrast, PT-r cells exhibited only fast inactivating, low-threshold Ca²⁺ channel currents with no steady state conductivity for Ca²⁺ at the resting potential of around -40 mV. We conclude that dihydropyridine-sensitive Ca²⁺ channels allow steady state transmembranous Ca²⁺ influx in C-cells, thereby increasing the cytosolic Ca²⁺ and CT secretion. Parathyroid cells, however, lack long-lasting Ca²⁺ channel currents and obviously sense the extracellular Ca²⁺ concentration by other mechanisms.

Recommended Citation

Scherubl, Hans; Brandi, Maria Luisa; and Hescheler, Jurgen (1992) "Extracellular Ca2+ Sensing in C-Cells and Parathyroid Cells," Henry Ford Hospital Medical Journal : Vol. 40 : No. 3 , 303-306.
Available at: https://scholarlycommons.henryford.com/hfhmedjournal/vol40/iss3/39