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J Physiol Sci. 2013 Jul;63(4):235-40. doi: 10.1007/s12576-013-0255-x. Epub 2013 Apr 16.

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

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Department of Nephrology and Hypertension, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan.


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.

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