Characterization of a volume-sensitive chloride current in rat osteoblast-like (ROS 17/2.8) cells

Gosling, Martin; Smith, J.W. and Poyner, David R. (1995). Characterization of a volume-sensitive chloride current in rat osteoblast-like (ROS 17/2.8) cells. Journal of Physiology, 485 (3), pp. 671-682.

Abstract

1. During osmotic swelling, cultured osteoblastic cells (ROS 17/2.8) exhibited activation of large amplitude Cl- currents in the whole-cell configuration of the patch-clamp technique. Effects of hypotonic shock on cell volume and membrane conductance were rapidly reversed on return to isotonic conditions. 2. Voltage command pulses in the range -80 to +50 mV produce instantaneous activation of Cl- currents. At potentials more positive than +50 mV the current exhibited time-dependent inactivation. The instantaneous current-voltage relationship was outwardly rectifying. 3. The anion permeability sequence of the induced current was SCN- (2.2) > I- (1.9) > Br- (1.5) > Cl- (1.0) > F- (0.8) > gluconate- (0.2). This corresponds to Eisenman's sequence I. 4. The volume-sensitive Cl- current was effectively inhibited by the Cl- channel blockers 4,4'-diisothiocyanatostilbene-2,2-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). Outward currents were more effectively suppressed by DIDS than inward currents. The concentrations for 50% inhibition (IC50) of outward and inward currents were 81 and 298 μM, respectively. NPPB was equally effective at inhibiting outward and inward currents (IC50 of 64 μM). The current was relatively insensitive to diphenylamine-2-carboxylate (DPC), 500 μM producing only 22.5 ± 4.0% inhibition. 5. Inhibitors of protein kinase A (H-89, 1 μM) and tyrosine kinase (tyrphostin A25, 200 μM) were without effect upon activation of Cl- currents in response to hypotonic shock. Under isotonic conditions, elevation of intracellular Ca2+ by ionomycin (1 μM) or activation of protein kinase C by 12-O-tetradecanoylphorbol 13-acetate (TPA, 0.1 μM) failed to evoke increases in basal Cl- conductance levels. 6. It is concluded that an outwardly rectifying Cl- conductance is activated upon osmotic swelling and may be involved in cell volume regulation of ROS 17/2.8 cells.

Publication DOI: http://www.scopus.com/inward/record.url?scp=0029011650&partnerID=8YFLogxK
Divisions: Life & Health Sciences > Pharmacy
Uncontrolled Keywords: animals,calcium,calcium channel blockers,cell membrane permeability,chloride channels,choline,cyclic,AMP-dependent protein,kinases,intracellular fluid,membrane potentials,osmosis,osteoblasts,osteosarcoma,patch-clamp techniques,protein-tyrosine kinases,rats,second messenger systems,tumor cells,cultured
Published Date: 1995-06-15

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