Contribution of chloride channels to volume regulation of cortical astrocytes

2003 ◽  
Vol 284 (6) ◽  
pp. C1460-C1467 ◽  
Author(s):  
Kimberly A. Parkerson ◽  
Harald Sontheimer
Keyword(s):  
Volume Regulation ◽  
Chloride Channels ◽  
Brain Regions ◽  
Niflumic Acid ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Relative Contribution ◽  
Cortical Astrocytes ◽  
Hippocampal Astrocytes

The objective of this study was to determine the relative contribution of Cl− channels to volume regulation of cultured rat cortical astrocytes after hypotonic cell swelling. Using a Coulter counter, we showed that cortical astrocytes regulate their cell volume by ∼60% within 45 min after hypotonic challenge. This volume regulation was supported when Cl− was replaced with Br−, NO[Formula: see text], methanesulfonate−, or acetate− but was inhibited when Cl− was replaced with isethionate− or gluconate−. Additionally, substitution of Cl− with I−completely blocked volume regulation. Volume regulation was unaffected by furosemide or bumetanide, blockers of KCl transport, but was inhibited by Cl− channel blockers, including 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), and niflumic acid. Surprisingly, the combination of Cd2+ with NPPB, DIDS, or niflumic acid inhibited regulation to a greater extent than any of these drugs alone. Volume regulation did not differ among astrocytes cultured from different brain regions, as cerebellar and hippocampal astrocytes exhibited behavior identical to that of cortical astrocytes. These data suggest that Cl− flux through ion channels rather than transporters is essential for volume regulation of cultured astrocytes in response to hypotonic challenge.

Dihydropyridine-sensitive cell volume regulation in proximal tubule: the calcium window

1990 ◽  
Vol 259 (6) ◽  
pp. F950-F960 ◽  
Author(s):  
N. A. McCarty ◽  
R. G. O'Neil
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Cell Swelling ◽  
Channel Blockers ◽  
Ca Channel ◽  
Hypotonic Solution ◽  
Dependent Manner ◽  
Intracellular Ca

The mechanism underlying the activation of hypotonic cell volume regulation was studied in rabbit proximal straight tubule (PST). When isolated non-perfused tubules were exposed to hypotonic solution, cells swelled rapidly and then underwent a regulatory volume decrease (RVD). The extent of regulation after swelling was highly dependent on extracellular Ca concentration ([Ca2+]o), with a half-maximal inhibition (K1/2) for [Ca2+]o of approximately 100 microM. RVD was blocked by the Ca-channel blockers verapamil, lanthanum, and the dihydropyridines (DHP) nifedipine and nitrendipine, implicating voltage-activated Ca channels in the RVD response. Using the fura-2 fluorescence-ratio technique, we observed that cell swelling caused a sustained rise in intracellular Ca ([Ca2+]i) only when [Ca2+]o was normal (1 mM) but not when [Ca2+]o was low (1-10 microM). Furthermore, external Ca was required early on during swelling to induce RVD. If RVD was initially blocked by reducing [Ca2+]o or by addition of verapamil during hypotonic swelling, volume regulation could only be restored by subsequently inducing Ca entry within the first 1 min or less of exposure to hypotonic solution. These data indicate a "calcium window" of less than 1 min, during which RVD is sensitive to Ca, and that part of the Ca-dependent mechanism responsible for achieving RVD undergoes inactivation after swelling. It is concluded that RVD in rabbit PST is modulated by Ca via a DHP-sensitive mechanism in a time-dependent manner.

Anion channel blockers inhibit swelling-activated anion, cation, and nonelectrolyte transport in HeLa cells

1996 ◽  
Vol 271 (2) ◽  
pp. C579-C588 ◽  
Author(s):  
J. A. Hall ◽  
J. Kirk ◽  
J. R. Potts ◽  
C. Rae ◽  
K. Kirk
Keyword(s):  
Hela Cells ◽  
Anion Channel ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Influx Rate ◽  
Cation Permeability ◽  
Transport Component ◽  
Selective Channel ◽  
Substrate Concentrations

The effect of osmotic cell swelling on the permeability of HeLa cells to a range of structurally unrelated solutes including taurine, sorbitol, thymidine, choline, and K+ (96Rb+) was investigated. For each solute tested, reduction in the osmolality of the medium from 300 to 200 mosmol/kgH2O caused a significant increase in the unidirectional influx rate. In each case, the osmotically activated transport component was nonsaturable up to external substrate concentrations of 50 mM. Inhibitors of the swelling-activated anion channel of HeLa cells [quinine, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, niflumate, 1,9-dideoxyforskolin, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and tamoxifen] blocked the osmotically activated influx of each of the different substrates tested, as well as the osmotically activated efflux of taurine and I-. Tamoxifen and NPPB were similarly effective at blocking the osmotically activated efflux of 96Rb+. The simplest of several hypotheses consistent with the data is that the osmotically activated transport of the different solutes tested here is via a swelling-activated anion-selective channel that has a significant cation permeability and a minimum pore diameter of 8-9 A.

Sustained outward current observed after I(to1) inactivation in rabbit atrial myocytes is a novel Cl- current

1992 ◽  
Vol 263 (6) ◽  
pp. H1967-H1971 ◽  
Author(s):  
D. Y. Duan ◽  
B. Fermini ◽  
S. Nattel
Keyword(s):  
Reversal Potential ◽  
Outward Current ◽  
Cell Voltage ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
K Channel ◽  
Transient Outward Current ◽  
Channel Blockers ◽  
Atrial Myocytes ◽  
K Concentration

In rabbit atrial myocytes, depolarization of the membrane results in a rapidly activating transient outward current (I(to)) that then decays to a sustained level. The sustained current (Isus) remains constant for at least 5 s during continued depolarization. The present study was designed to identify the ionic mechanism underlying Isus with the use of whole cell voltage-clamp techniques. After exposure to 2 mM 4-aminopyridine (4-AP), the 4-AP-sensitive transient outward current (I(to1)) was abolished, but Isus was unaffected. Isus was not blocked by the K+ channel blockers tetraethylammonium chloride and Ba2+, was not changed by increasing superfusate K+ concentration, and was still present when K+ was replaced by Cs+ in both the superfusate and the pipette. Isus was significantly reduced by the Cl- transport blockers 4-acetamido-4'-isothiocyanatostilbene-2.2'-disulfonic acid and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. The current-voltage relations of Isus showed outward rectification, and the reversal potential of Isus shifted with changes in the transmembrane Cl- gradient in the fashion expected for a Cl- current. We conclude that Isus in rabbit atrium is due to a noninactivating Cl- current which, unlike previously described cardiac Cl- currents, is manifest in the absence of exogenous stimulators of adenosine 3',5'-cyclic monophosphate formation, cytosolic Ca2+ transients, or cell swelling.

Chloride current activated by swelling in retinal pigment epithelium cells

1993 ◽  
Vol 265 (4) ◽  
pp. C1037-C1045 ◽  
Author(s):  
L. M. Botchkin ◽  
G. Matthews
Keyword(s):  
Retinal Pigment Epithelium ◽  
Fluid Transport ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Ionic Composition ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Subretinal Space ◽  
Channel Blockers ◽  
Membrane Stretch

A membrane conductance activated by cell swelling was characterized in cells of the retinal pigment epithelium (RPE). Manipulations of internal and external Cl concentration revealed that the conductance is permeable to Cl and somewhat permeable to the gluconate anion used for Cl substitution (ratio of gluconate to Cl permeability approximately 0.1). The conductance was blocked by the Cl channel blockers 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid in a manner consistent with open-channel blockade. Both the onset and recovery of the Cl current following a transient increase in cell volume were slow. This suggests that activation of the current depends on some internal signal rather than directly on membrane stretch. Experiments to examine a possible role for intracellular Ca concentration ([Ca]i) in regulation of the current demonstrated that an increase in [Ca]i was not involved in the linkage between swelling and Cl current; activation of the current was unaffected by the calcium-buffering conditions, the current could not be activated by large increases in [Ca]i elicited by ionomycin, and no changes in [Ca]i were observed to be associated with swelling. RPE cells normally experience changes in the volume and ionic composition of the extracellular subretinal space during changes in illumination conditions; therefore, the volume-sensitive Cl conductance may play a role in volume regulation in the RPE in response to these extracellular changes and/or in transepithelial fluid transport.

scholarly journals Distinct Expression/Function of Potassium and Chloride Channels Contributes to the Diverse Volume Regulation in Cortical Astrocytes of GFAP/EGFP Mice

PLoS ONE ◽  
2012 ◽  
Vol 7 (1) ◽  
pp. e29725 ◽  
Author(s):  
Jana Benesova ◽  
Vendula Rusnakova ◽  
Pavel Honsa ◽  
Helena Pivonkova ◽  
David Dzamba ◽  
...  
Keyword(s):  
Volume Regulation ◽  
Chloride Channels ◽  
Cortical Astrocytes

ATP Released From Astrocytes During Swelling Activates Chloride Channels

2003 ◽  
Vol 89 (4) ◽  
pp. 1870-1877 ◽  
Author(s):  
Mark Darby ◽  
J. Brent Kuzmiski ◽  
William Panenka ◽  
Denise Feighan ◽  
Brian A. MacVicar
Keyword(s):  
Chloride Channels ◽  
Purinergic Receptors ◽  
Neuronal Excitability ◽  
Regulatory Volume Decrease ◽  
Atp Release ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
P2x7 Receptors ◽  
Whole Cell Patch Clamp ◽  
Cultured Astrocytes

ATP release from astrocytes contributes to calcium ([Ca2+]) wave propagation and may modulate neuronal excitability. In epithelial cells and hepatocytes, cell swelling causes ATP release, which leads to the activation of a volume-sensitive Cl− current ( I Cl,swell) through an autocrine pathway involving purinergic receptors. Astrocyte swelling is counterbalanced by a regulatory volume decrease, involving efflux of metabolites and activation of I Cl,swell and K+currents. We used whole cell patch-clamp recordings in cultured astrocytes to investigate the autocrine role of ATP in the activation of I Cl,swell by hypo-osmotic solution (HOS). Apyrase, an ATP/ADP nucleotidase, inhibited HOS-activated I Cl,swell, whereas ATP and the P2Y agonists, ADPβS and ADP, induced Cl− currents similar to I Cl,swell. Neither the P2U agonist, UTP nor the P2X agonist, α,β-methylene ATP, were effective. BzATP was less effective than ATP, suggesting that P2X7 receptors were not involved. P2 purinergic antagonists, suramin, RB2, and pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) reversibly inhibited activation of I Cl,swell, suggesting that ATP-activated P2Y1 receptors. Thus ATP release mediates I Cl,swell in astrocytes through the activation of P2Y1-like receptors. The multidrug resistance protein (MRP) transport inhibitors probenicid, indomethacin, and MK-571 all potently inhibited I Cl.swell. ATP release from astrocytes in HOS was observed directly using luciferin-luciferase and MK-571 reversibly depressed this HOS-induced ATP efflux. We conclude that ATP release via MRP and subsequent autocrine activation of purinergic receptors contributes to the activation of I Cl,swell in astrocytes by HOS-induced swelling.

scholarly journals Estradiol activates chloride channels via estrogen receptor-α in the cell membranes of osteoblasts

2017 ◽  
Vol 313 (2) ◽  
pp. C162-C172 ◽  
Author(s):  
Zhiqin Deng ◽  
Shuang Peng ◽  
Yanfang Zheng ◽  
Xiaoya Yang ◽  
Haifeng Zhang ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Cell Membrane ◽  
Chloride Channels ◽  
Estrogen Receptor Α ◽  
Disulfonic Acid ◽  
Equilibrium Potential ◽  
Channel Blockers ◽  
Osteoblast Activity ◽  
Osteoblast Cell Line ◽  
17Β Estradiol

Estrogen plays important roles in regulation of bone formation. Cl− channels in the ClC family are expressed in osteoblasts and are associated with bone physiology and pathology, but the relationship between Cl− channels and estrogen is not clear. In this study the action of estrogen on Cl− channels was investigated in the MC3T3-E1 osteoblast cell line. Our results show that 17β-estradiol could activate a current that reversed at a potential close to the Cl− equilibrium potential, with a sequence of anion selectivity of I− > Br− > Cl− > gluconate, and was inhibited by the Cl− channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoate and 4,4′-diisothiocyano-2,2′-stilbene disulfonic acid. Knockdown of ClC-3 Cl− channel expression by a specific small interfering RNA to ClC-3 attenuated activation of the 17β-estradiol-induced Cl− current. Extracellular application of membrane-impermeable 17β-estradiol-albumin conjugates activated a similar current. The estrogen-activated Cl− current could be inhibited by the estrogen receptor (ER) antagonist fulvestrant (ICI 182780). The selective ERα agonist, but not ERβ agonist, activated a Cl− current similar to that induced by 17β-estradiol. Silencing ERα expression prevented activation of estrogen-induced currents. Immunofluorescence and coimmunoprecipitation experiments demonstrated that ClC-3 Cl− channels and ERα were colocalized and closely related in cells. Estrogen promoted translocation of ClC-3 and ERα to the cell membrane from the nucleus. In conclusion, our findings show that Cl− channels can be activated by estrogen via ERα on the cell membrane and suggest that the ClC-3 Cl− channel may be one of the targets of estrogen in the regulation of osteoblast activity.

cAMP- and swelling-activated chloride conductance in rat hepatocytes

1996 ◽  
Vol 271 (1) ◽  
pp. C112-C120 ◽  
Author(s):  
X. J. Meng ◽  
S. A. Weinman
Keyword(s):  
Rat Hepatocytes ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Ionic Selectivity ◽  
Patch Clamp Technique ◽  
Isolated Rat Hepatocytes ◽  
Pipette Solution ◽  
Set Point ◽  
Cl Conductance

An outwardly rectifying Cl- conductance was identified in primary isolated rat hepatocytes, and the whole cell patch-clamp technique was used to characterize its properties and mechanisms of activation. With symmetrical Cl(-)-containing solutions on both sides and adenosine 3',5'-cyclic monophosphate (cAMP; 100 microM) in the pipette solution, a large outwardly rectifying conductance (1,014 +/- 153 pS/pF, n = 20) developed in all cells within 3 min. This cAMP-activated conductance was highly anion selective and slowly inactivated at voltages > 80 mV. It was completely inhibited by the anion channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (200 microM, n = 6) and partially inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (150 microM, n = 7). It displayed a halide selectivity of I- > Br- > Cl-. In the absence of cAMP, a functionally similar conductance was activated by cell swelling. Reduction of bath osmolality from 300 to 250 mosmol/kg increased membrane conductance from 64 +/- 16.4 to 487 +/- 23 pS/pF (n = 4). This swelling-activated conductance was also highly anion selective and had identical halide selectivity and blocker sensitivity as the cAMP-activated conductance. Although cell swelling was not necessary for cAMP activation, cell shrinkage with hyperosmotic bath (350 mosmol/kg), either before or after exposure to cAMP, inhibited the cAMP-activated conductance. By the determination of conductance as a function of bath osmolality in the presence and absence of cAMP, it was observed that cAMP shifted the osmotic set point for conductance activation without changing either the maximum or minimum conductance. In conclusion, both cAMP and cell swelling activate a large outwardly rectifying Cl- conductance in rat hepatocytes. Its ionic selectivity and sensitivity to channel blockers are identical to those seen for swelling-activated Cl- conductances in many cell types. The conductive properties are not those of cystic fibrosis transmembrane conductance regulator-mediated Cl- conductance. cAMP appears to activate this conductance by altering the volume set point of a swelling-activated channel.

Volume-associated osmolyte fluxes in cell lines with or without the anion exchanger

1995 ◽  
Vol 269 (5) ◽  
pp. C1280-C1286 ◽  
Author(s):  
R. Sanchez-Olea ◽  
C. Fuller ◽  
D. Benos ◽  
H. Pasantes-Morales
Keyword(s):  
Amino Acid ◽  
Cell Lines ◽  
Anion Exchanger ◽  
Chinese Hamster ◽  
Anion Channel ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Cell Type ◽  
Amino Acid Efflux

To investigate the involvement of a red cell-type anion exchanger in the volume-sensitive amino acid release, the hyposmolarity-evoked release of D-[3H]aspartate and [3H]taurine was examined in three cell lines: 1) wild-type Chinese hamster ovary (CHO-K1) cells, expressing an anion exchanger activity (Cl-/SO4(2-)) functionally similar to the erythroid band 3; 2) a mutant CHO cell type (CHO 605) lacking this anion exchanger activity; and 3) 293 cells in which the Cl-/HCO3(-) anion exchanger is absent. All cell types accumulated D-[3H]aspartate and [3H]taurine under isosmotic conditions, and, similarly, in the three cell lines, cell swelling evoked by hyposmolarity induced a rapid and transient increase in the amino acid efflux. Blockers of the anion exchanger and/or Cl- channels [niflumic acid, dipyridamole, diphenylamine-2-carboxylate,5-nitro-2-(3-phenylpropylamino)-benzoi c acid, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid] were potent inhibitors of amino acid efflux in the three cell lines. 125I- efflux, used as a marker for Cl- fluxes, was also markedly increased in response to cell swelling in all cell lines, and this efflux was inhibited by the anion exchanger/Cl- channel blockers. These results do not support a role for an anion exchanger in the hyposmolarity-induced amino acid efflux and suggest that amino acids and Cl- may be transported by the same or a similar mechanism, presumably an anion channel-like structure.

scholarly journals Glial Chloride Homeostasis Under Transient Ischemic Stress

2021 ◽  
Vol 15 ◽  
Author(s):  
Miriam Engels ◽  
Manu Kalia ◽  
Sarah Rahmati ◽  
Laura Petersilie ◽  
Peter Kovermann ◽  
...  
Keyword(s):  
Glial Cell ◽  
Excitatory Amino Acid ◽  
Brain Slices ◽  
Brain Regions ◽  
Cell Swelling ◽  
Channel Inhibition ◽  
Outward Transport ◽  
Chloride Accumulation ◽  
Hippocampal Astrocytes ◽  
Energy Deprivation

High water permeabilities permit rapid adjustments of glial volume upon changes in external and internal osmolarity, and pathologically altered intracellular chloride concentrations ([Cl–]int) and glial cell swelling are often assumed to represent early events in ischemia, infections, or traumatic brain injury. Experimental data for glial [Cl–]int are lacking for most brain regions, under normal as well as under pathological conditions. We measured [Cl–]int in hippocampal and neocortical astrocytes and in hippocampal radial glia-like (RGL) cells in acute murine brain slices using fluorescence lifetime imaging microscopy with the chloride-sensitive dye MQAE at room temperature. We observed substantial heterogeneity in baseline [Cl–]int, ranging from 14.0 ± 2.0 mM in neocortical astrocytes to 28.4 ± 3.0 mM in dentate gyrus astrocytes. Chloride accumulation by the Na+-K+-2Cl– cotransporter (NKCC1) and chloride outward transport (efflux) through K+-Cl– cotransporters (KCC1 and KCC3) or excitatory amino acid transporter (EAAT) anion channels control [Cl–]int to variable extent in distinct brain regions. In hippocampal astrocytes, blocking NKCC1 decreased [Cl–]int, whereas KCC or EAAT anion channel inhibition had little effect. In contrast, neocortical astrocytic or RGL [Cl–]int was very sensitive to block of chloride outward transport, but not to NKCC1 inhibition. Mathematical modeling demonstrated that higher numbers of NKCC1 and KCC transporters can account for lower [Cl–]int in neocortical than in hippocampal astrocytes. Energy depletion mimicking ischemia for up to 10 min did not result in pronounced changes in [Cl–]int in any of the tested glial cell types. However, [Cl–]int changes occurred under ischemic conditions after blocking selected anion transporters. We conclude that stimulated chloride accumulation and chloride efflux compensate for each other and prevent glial swelling under transient energy deprivation.

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