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Extracellular Ca 2+ Increases Cytosolic Free Ca 2+ in Freshly Isolated Rat Odontoblasts
Author(s) -
Guo Liang,
Davidson Robert M.
Publication year - 1999
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.1999.14.8.1357
Subject(s) - calcium , extracellular , t type calcium channel , calcium in biology , voltage dependent calcium channel , chemistry , trpv6 , intracellular , biophysics , dantrolene , thapsigargin , fura 2 , endocrinology , cytosol , medicine , biochemistry , biology , organic chemistry , enzyme
Recent evidence suggests that extracellular Ca 2+ may modulate cell function in mineralized tissue. To determine whether dentinogenic cells, in particular, are sensitive to extracellular Ca 2+ , fura‐2 microfluorometry was used to monitor intracellular calcium levels in odontoblasts freshly isolated from rat incisor. In response to applications of 0.5–4.0 mM extracellular calcium (CaCl 2 ), most odontoblasts (84%; 107/128) showed an increase in intracellular calcium. For the majority of these cells (70%; 75/107), the typical response was biphasic; there was an initial, transient increase in intracellular calcium which reached peak levels within 30–50 s and decayed rapidly, followed by a slower (> 300 s) recovery toward basal levels. In general, the response of these cells to calcium was repeatable and the mean calcium concentration for the half‐maximal response was ∼1.3 mM. This effect could be partially blocked by either 200 μM lanthanum, a nonspecific blocker of Ca 2+ channels, or 20 μM dantrolene, a potent inhibitor of Ca 2+ release from internal stores. Used in combination, lanthanum, and dantrolene nearly abolished the calcium response completely. In addition, this response was sensitive to the dihydropyridine‐sensitive calcium channel blocking agent nicardipine (60 μM), indicating a role for voltage‐gated calcium channels during these events. These results show that odontoblasts respond to external calcium through mechanisms involving both influx of external calcium as well as release of calcium from internal stores and suggest a role for extracellular calcium in regulating the function of these cells.