Calcium influx and release in isolated rat osteoclasts.

Journal article

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.

Authors: Shankar, V; Huang, C; Adebanjo, O; Pazianas, M; Zaidi, M

• Journal: Experimental physiology
• Volume: 79
• Issue: 4
• Pages: 537-545
• Publication date: 1994-07-01
• EISSN: 1469-445X
• ISSN: 0958-0670
• Language: English
• Keywords: Osteoclasts; Cytosol; Egtazic Acid; Ion Transport; Rats; Calcium; Ionomycin; Rats, Wistar; Potassium; Membrane Potentials; Animals