| Abstrakt: |
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 ORClcurrent 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 ORClcurrent without hypotonic stress, but inhibited activation of the ORClcurrent by hypotonic stimulation. The hypotonically activated ORClcurrent was unaffected by a non‐actin‐depolymerizing cytochalasin, chaetoglobosin C, but partially inhibited by deoxyribonuclease I.4Removal of extracellular Ca2+inhibited activation of the ORClcurrent by hypotonic shock, but did not reduce the current once activated. The hypotonically activated ORClcurrent was partially decreased by intracellular dialysis with 20 mmEGTA.5With 10 mmCa2+in the extracellular medium, the ORClcurrent was activated in response to more minor decreases in osmolarity than with 1 mmCa2+. 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 ORClchannel of murine osteoclasts, and that the activating process is modified by multiple intracellular factors (pH, ATP and actin cytoskeletal organization). |
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