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Calcium influx and release in isolated rat osteoclasts
Author(s) -
Shankar VS,
Huang CL,
Adebanjo OA,
Pazianas M,
Zaidi M
Publication year - 1994
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1994.sp003786
Subject(s) - ionomycin , extracellular , cytosol , intracellular , egta , fura 2 , calcium , biophysics , ionophore , chemistry , microbiology and biotechnology , medicine , biochemistry , biology , enzyme
Intracellular and extracellular sources of cytosolic [Ca2+] elevation in isolated rat osteoclasts were explored by a comparison of fura‐2 signals in response to application of the Ca2+ ionophore, ionomycin, in Ca(2+)‐containing and in Ca(2+)‐free bathing solutions. Cytosolic [Ca2+] transients persisted in osteoclasts bathed in Ca(2+)‐free, EGTA‐containing solutions. They consisted of a peak cytosolic [Ca2+bd elevation followed by a full decay to baseline and were refractory to manipulations of surface membrane potential through changes in extracellular [K+]. They disappeared upon intracellular Ca2+ store depletion through repeated ionophore applications. They were therefore attributable solely to intracellularly stored Ca2+. In contrast, the fura‐2 peaks in osteoclasts exposed to Ca(2+)‐containing solutions decayed to sustained levels. Cytosolic [Ca2+] responses then persisted with repeated ionomycin application. These latter phenomena are accordingly attributable to extracellular Ca2+ entry. Finally, restoration of extracellular [Ca2+] to 1.25 mM following the depletion of intracellular Ca2+ stores by treatment with ionomycin elicited a cytosolic [Ca2+] 'overshoot' consistent with capacitative Ca2+ entry via a cytosolic route. These results demonstrate a refillable intracellular source of cytosolic Ca2+ that could function in osteoclastic regulation.