Detection of dihydropyridine- and voltage-sensitive intracellular Ca(2+) signals in normal human parathyroid cells.

We recently showed dihydropyridine- and voltage-sensitive Ca(2+) entry in cultured parathyroid cells from patients with secondary hyperparathyroidism. To determine whether normal parathyroid cells have a similar extracellular Ca(2+) entry system, cells were isolated from normal (non-hyperplastic) human parathyroid glands. Fluorescence signals related to the cytoplasmic Ca(2+) concentration ([Ca(2+)]I) were examined in these cells. Cells loaded with fluo-3/AM showed a transient increase in fluorescence (Ca(2+) transient) following a 10-s exposure to a 150 mM K(+) solution in the presence of millimolar concentrations of external Ca(2+). The Ca(2+) transient was reduced by dihydropyridine antagonists or 0.5 mM Cd(2+), but enhanced by FPL-64176, an L-type Ca(2+)-channel agonist. Ca(2+) transients induced by the 10-s exposure to 3.0 mM extracellular Ca(2+) ([Ca(2+)]o) were also inhibited by dihydropyridine antagonists or 0.5 mM Cd(2+). These results provide the first evidence that normal human parathyroid cells express a dihydropyridine-sensitive Ca(2+) entry system that may be involved in the [Ca(2+)]o-induced change in [Ca(2+)]I. This system might provide a compensatory pathway for negative feedback regulation of parathyroid hormone secretion under physiological conditions.

Citation

Rinako Iida, Keitaro Yokoyama, Ichiro Ohkido, Isao Tabei, Hiroshi Takeyama, Akifumi Suzuki, Toshiaki Shibasaki, Douchi Matsuba, Norio Suda, Tatsuo Hosoya. Detection of dihydropyridine- and voltage-sensitive intracellular Ca(2+) signals in normal human parathyroid cells. The journal of physiological sciences : JPS. 2013 Jul;63(4):235-40

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PMID: 23588930

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