Synergetic activation of outwardly rectifying Cl− currents by hypotonic stress and external Ca2+ in murine osteoclasts
Article first published online: 8 SEP 2004
The Journal of Physiology
Volume 515, Issue 1, pages 157–168, February 1999
How to Cite
Sakai, H., Nakamura, F. and Kuno, M. (1999), Synergetic activation of outwardly rectifying Cl− currents by hypotonic stress and external Ca2+ in murine osteoclasts. The Journal of Physiology, 515: 157–168. doi: 10.1111/j.1469-7793.1999.157ad.x
- Issue published online: 8 SEP 2004
- Article first published online: 8 SEP 2004
- (Received 24 August 1998; accepted after revision 03 November 1998)
- 1An outwardly rectifying Cl− (ORCl) current of murine osteoclasts was activated by hypotonic stimulation. The current was characterized by rapid activation, little inactivation, strong outward rectification, blockage by DIDS and permeability to organic acids (pyruvate and glutamate).
- 2The hypotonically activated ORCl current was inhibited by intracellular dialysis with an ATP-free pipette solution, but not by replacement of ATP with a poorly hydrolysable ATP analogue adenosine 5′-O-(3-thiotriphosphate). The current amplitude was reduced when intracellular alkalinity increased over the pH range 6.6–8.0.
- 3Intracellular application of cytochalasin D occasionally activated the ORCl current without hypotonic stress, but inhibited activation of the ORCl current by hypotonic stimulation. The hypotonically activated ORCl current was unaffected by a non-actin-depolymerizing cytochalasin, chaetoglobosin C, but partially inhibited by deoxyribonuclease I.
- 4Removal of extracellular Ca2+ inhibited activation of the ORCl current by hypotonic shock, but did not reduce the current once activated. The hypotonically activated ORCl current was partially decreased by intracellular dialysis with 20 mm EGTA.
- 5With 10 mm Ca2+ in the extracellular medium, the ORCl current was activated in response to more minor decreases in osmolarity than with 1 mm Ca2+. The increased sensitivity to hypotonicity was mimicked by increasing the intracellular Ca2+ level (pCa 6.5).
- 6These results suggest that hypotonic stimulation and a rise in the extracellular Ca2+ level synergistically activate the ORCl channel of murine osteoclasts, and that the activating process is modified by multiple intracellular factors (pH, ATP and actin cytoskeletal organization).