title: Detection of dihydropyridine- and voltage-sensitive intracellular Ca(2+) signals in normal human parathyroid cells.
abstract: 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.
authors.affiliation: Department of Nephrology and Hypertension, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan. rinako@jikei.ac.jp
authors.forename: Rinako
authors.initials: R
authors.lastname: Iida
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ohkido
authors.forename: Isao
authors.initials: I
authors.lastname: Tabei
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeyama
authors.forename: Akifumi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Shibasaki
authors.forename: Douchi
authors.initials: D
authors.lastname: Matsuba
authors.forename: Norio
authors.initials: N
authors.lastname: Suda
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Hosoya
mesh_terms: D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000187:drug effects; D020013:Calcium Signaling / Q000502:physiology*; D004095:Dihydropyridines / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D009529:Nicardipine / Q000494:pharmacology; D010280:Parathyroid Glands / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; C038806:1,4-dihydropyridine; D009529:Nicardipine