Outwardly rectifying chloride current in rabbit osteoclasts is activated by hyposmotic stimulation
1. We characterized chloride currents in freshly isolated rabbit osteoclasts using whole-cell and single channel patch-clamp recording configurations. Depolarization activated an outwardly rectifying current in 40-50% of cells, distinct from the inwardly rectifying K+ current we have previously repo...
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Published in | The Journal of physiology Vol. 475; no. 3; pp. 377 - 389 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Oxford
The Physiological Society
15.03.1994
Blackwell |
Subjects | |
Online Access | Get full text |
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Summary: | 1. We characterized chloride currents in freshly isolated rabbit osteoclasts using whole-cell and single channel patch-clamp
recording configurations. Depolarization activated an outwardly rectifying current in 40-50% of cells, distinct from the inwardly
rectifying K+ current we have previously reported in osteoclasts. 2. The outwardly rectifying current persisted under conditions
where all K+ currents were blocked. Furthermore, the outward current was reversibly inhibited by Cl- transport blockers 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic
acid (SITS); 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS); 4,4'-dinitrostilbene-2,2'-disulphonic acid (DNDS);
and niflumic acid. The blocked current had a reversal potential close to the predicted chloride equilibrium potential and
was dependent on the chloride concentration gradient. 3. In those osteoclasts in which outwardly rectifying current was not
initially apparent, exposure to hyposmotic extracellular solution resulted in its reversible activation. The induced current
was due to Cl-, based on its reversal close to the chloride equilibrium potential and sensitivity to blockade by Cl- channel
inhibitors. The hyposmotically induced current could be activated in Ca(2+)-free solutions containing 0.2 mM EGTA. 4. When
studied in the current-clamp configuration, hyposmotic stimulation caused depolarization from -76 +/- 5 to -5 +/- 6 mV (mean
+/- S.D., n = 7). 5. Unitary Cl- currents were recorded in the cell-attached patch configuration at positive potentials. Single
channels had a slope conductance of 19 +/- 3 pS (n = 5). Reduction of the external [Cl-] shifted the current-voltage relationship
in the positive direction, supporting the conclusion that these were Cl- currents. Like the whole-cell currents, single channel
Cl- currents were activated by exposure of cells to hyposmotic bathing solution. 6. We conclude that rabbit osteoclasts express
an outwardly rectifying Cl- current that can be activated by osmotic stress. Cl- channels may play a role in cell volume regulation
and may also provide conductive pathways for dissipating the potential difference that arises from electrogenic proton transport
during bone resorption. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1994.sp020079 |