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Extracellular Ca2+ sensing in C-cells and parathyroid cells
H Scherubl1, M L Brandi, J Hescheler
1Pharmacokologisches Institut, Freie Universitat Berlin, Berlin, Germany.
Henry Ford Hospital Medical Journal
|January 1, 1992
Summary
C-cells use voltage-dependent calcium channels for calcium influx, stimulating calcitonin secretion. Parathyroid cells lack these channels, suggesting alternative mechanisms for sensing extracellular calcium.
Area of Science:
- Endocrinology
- Cell Physiology
- Molecular Biology
Background:
- C-cells and parathyroid cells regulate extracellular calcium levels.
- Calcium-dependent secretion of calcitonin (CT) and parathyroid hormone involves intracellular calcium changes.
Purpose of the Study:
- To investigate if calcium influx via voltage-dependent calcium channels links extracellular to intracellular calcium sensing.
- To compare calcium channel activity in C-cells and parathyroid cells.
Main Methods:
- Patch clamp technique applied to rMTC 44-2 (C-cell) and PT-r (parathyroid) cell lines.
- Analysis of ion flux through voltage-dependent calcium channels.
Main Results:
- rMTC C-cells possess dihydropyridine-sensitive, high-threshold calcium channels active at resting potential.
- Extracellular divalent cations and Bay K 8644 stimulated steady-state ion influx in C-cells.
- PT-r parathyroid cells showed only fast-inactivating, low-threshold calcium currents with no steady-state influx at resting potential.
Conclusions:
- Dihydropyridine-sensitive calcium channels facilitate steady-state calcium influx in C-cells, enhancing cytosolic calcium and CT secretion.
- Parathyroid cells likely utilize different mechanisms for extracellular calcium sensing due to the absence of sustained calcium channel currents.