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Olde Hanhof CJA, Yousef Yengej FA, Rookmaaker MB, Verhaar MC, van der Wijst J, Hoenderop JG. Modeling Distal Convoluted Tubule (Patho)Physiology: An Overview of Past Developments and an Outlook Toward the Future. Tissue Eng Part C Methods 2021; 27:200-212. [PMID: 33544049 DOI: 10.1089/ten.tec.2020.0345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The kidneys are essential for maintaining electrolyte homeostasis. Blood electrolyte composition is controlled by active reabsorption and secretion processes in dedicated segments of the kidney tubule. Specifically, the distal convoluted tubule (DCT) and connecting tubule are important for regulating the final excretion of sodium, magnesium, and calcium. Studies unravelling the specific function of these segments have greatly improved our understanding of DCT (patho)physiology. Over the years, experimental models used to study the DCT have changed and the field has advanced from early dissection studies with rats and rabbits to the use of various transgenic mouse models. Developments in dissection techniques and cell culture methods have resulted in immortalized mouse DCT cell lines and made it possible to specifically obtain DCT fragments for ex vivo studies. However, we still do not fully understand the complex (patho)physiology of this segment and there is need for advanced human DCT models. Recently, kidney organoids and tubuloids have emerged as new complex cell models that provide excellent opportunities for physiological studies, disease modeling, drug discovery, and even personalized medicine in the future. This review presents an overview of cell models used to study the DCT and provides an outlook on kidney organoids and tubuloids as model for DCT (patho)physiology. Impact statement This study provides a detailed overview of past and future developments on cell models used to study kidney (patho)physiology and specifically the distal convoluted tubule (DCT) segment. Hereby, we highlight the need for an advanced human cell model of this segment and summarize recent advances in the field of kidney organoids and tubuloids with a focus on DCT properties. The findings reported in this review are significant for future developments toward an advanced human model of the DCT that will help to increase our understanding of DCT (patho)physiology.
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Affiliation(s)
- Charlotte J A Olde Hanhof
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Fjodor A Yousef Yengej
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, The Netherlands.,Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Maarten B Rookmaaker
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marianne C Verhaar
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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Affiliation(s)
- H Barrière
- UMR CNRS 6548, Université de Nice-Sophia Antipolis, 06108 Nice Cedex 2, France
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Barrière H, Rubera I, Belfodil R, Tauc M, Tonnerieux N, Poujeol C, Barhanin J, Poujeol P. Swelling-activated chloride and potassium conductance in primary cultures of mouse proximal tubules. Implication of KCNE1 protein. J Membr Biol 2003; 193:153-70. [PMID: 12962276 DOI: 10.1007/s00232-003-2014-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2002] [Indexed: 10/26/2022]
Abstract
Volume-sensitive chloride and potassium currents were studied, using the whole-cell clamp technique, in cultured wild-type mouse proximal convoluted tubule (PCT) epithelial cells and compared with those measured in PCT cells from null mutant kcne1 -/- mice. In wild-type PCT cells in primary culture, a Cl- conductance activated by cell swelling was identified. The initial current exhibited an outwardly rectifying current-voltage (I-V) relationship, whereas steady-state current showed decay at depolarized membrane potentials. The ion selectivity was I- > Br- > Cl- > > gluconate. This conductance was sensitive to 1 mM 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 0.1 mM 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and 1 mM diphenylamine-2-carboxylate (DPC). Osmotic stress also activated K+ currents. These currents are time-independent, activated at depolarized potentials, and inhibited by 0.5 mM quinidine, 5 mM barium, and 10 microM clofilium but are insensitive to 1 mM tetraethylammonium (TEA), 10 nM charybdotoxin (CTX), and 10 microM 293B. In contrast, the null mutation of kcne1 completely impaired volume-sensitive chloride and potassium currents in PCT. The transitory transfection of kcne1 restores both Cl- and K+ swelling-activated currents, confirming the implication of KCNE1 protein in the cell-volume regulation in PCT cells in primary cultures.
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Affiliation(s)
- H Barrière
- UMR CNRS 6548, Université de Nice-Sophia Antipolis, 06108 Nice Cedex 2, France
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Lourdel S, Paulais M, Marvao P, Nissant A, Teulon J. A chloride channel at the basolateral membrane of the distal-convoluted tubule: a candidate ClC-K channel. J Gen Physiol 2003; 121:287-300. [PMID: 12668733 PMCID: PMC2217373 DOI: 10.1085/jgp.200208737] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The distal-convoluted tubule (DCT) of the kidney absorbs NaCl mainly via an Na+-Cl- cotransporter located at the apical membrane, and Na+, K+ ATPase at the basolateral side. Cl- transport across the basolateral membrane is thought to be conductive, but the corresponding channels have not yet been characterized. In the present study, we investigated Cl- channels on microdissected mouse DCTs using the patch-clamp technique. A channel of approximately 9 pS was found in 50% of cell-attached patches showing anionic selectivity. The NPo in cell-attached patches was not modified when tubules were preincubated in the presence of 10-5 M forskolin, but the channel was inhibited by phorbol ester (10-6 M). In addition, NPo was significantly elevated when the calcium in the pipette was increased from 0 to 5 mM (NPo increased threefold), or pH increased from 6.4 to 8.0 (NPo increased 15-fold). Selectivity experiments conducted on inside-out patches showed that the Na+ to Cl- relative permeability was 0.09, and the anion selectivity sequence Cl(-)--I(-) > Br(-)--NO3(-) > F(-). Intracellular NPPB (10-4 M) and DPC (10-3 M) blocked the channel by 65% and 80%, respectively. The channel was inhibited at acid intracellular pH, but intracellular ATP and PKA had no effect. ClC-K Cl- channels are characterized by their sensitivity to the external calcium and to pH. Since immunohistochemical data indicates that ClC-K2, and perhaps ClC-K1, are present on the DCT basolateral membrane, we suggest that the channel detected in this study may belong to this subfamily of the ClC channel family.
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Affiliation(s)
- Stéphane Lourdel
- Laboratoire de Physiologie, CNRS-FRE 2468, Institut des Cordeliers, 15 rue de l'Ecole de Médecine, 75270 Paris CEDEX 06, France
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Duong Van Huyen JP, Bens M, Teulon J, Vandewalle A. Vasopressin-stimulated chloride transport in transimmortalized mouse cell lines derived from the distal convoluted tubule and cortical and inner medullary collecting ducts. Nephrol Dial Transplant 2001; 16:238-45. [PMID: 11158395 DOI: 10.1093/ndt/16.2.238] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The fine control of NaCl absorption takes place in the distal parts of the renal tubule, but the regulation of Cl(-) transport in this region has not been fully elucidated. We have analysed the effects of dD-arginine vasopressin (dDAVP) on Cl(-) fluxes in cultured mouse distal convoluted tubule (mpkDCT), cortical collecting duct (mpkCCD) and inner medullary collecting duct (mpkIMCD) cell lines. METHODS RT-PCR and Western blotting were used to detect the amiloride-sensitive sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR) mRNAs and protein in cultured mpkDCT, mpkCCD and mpkIMCD cells. Cl(-) fluxes were analysed by measuring the short-circuit current (I(sc)) and bidirectional (36)Cl(-) fluxes on confluent cells grown on filters. RESULTS All three cell lines expressed ENaC and CFTR and had I(sc) stimulated by dDAVP. The rise in I(sc) caused by dDAVP (10(-8) M) was inhibited by amiloride, and to a lesser extent by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) in all three cell lines. The dDAVP-dependent I(sc) measured under apical Na(+)-free condition was reduced by Cl(-) channel blockers with a profile (NPPB>glibenclamide>DIDS), similar to that for rat CFTR. dDAVP stimulated the apical-to-basal (36)Cl(-) flux and to a lesser extent the basal-to-apical (36)Cl(-) flux under open-circuit condition in all three cultured cell lines. Adding NPPB to the apical side reduced the basal-to-apical (36)Cl(-) flux but not the opposite (36)Cl(-) flux from dDAVP-treated cells. CONCLUSION These results indicate that dDAVP stimulates the bi-directional flux of Cl(-), resulting in net Cl(-)absorption, in these cultured mouse distal and collecting duct cells. I(sc) experiments also suggest the presence of a minor component of electrogenic Cl(-) secretion, possibly mediated by CFTR.
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Affiliation(s)
- J P Duong Van Huyen
- Institut National de la Santé et de la Recherche Médicale, Unité 478, Institut Fédératif de Recherche 02, Faculté de Médecine Xavier Bichat, Paris, France
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Rubera I, Tauc M, Bidet M, Verheecke-Mauze C, De Renzis G, Poujeol C, Cuiller B, Poujeol P. Extracellular ATP increases [Ca(2+)](i) in distal tubule cells. II. Activation of a Ca(2+)-dependent Cl(-) conductance. Am J Physiol Renal Physiol 2000; 279:F102-11. [PMID: 10894792 DOI: 10.1152/ajprenal.2000.279.1.f102] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We characterized Cl(-) conductance activated by extracellular ATP in an immortalized cell line derived from rabbit distal bright convoluted tubule (DC1). (125)I(-) efflux experiments showed that ATP increased (125)I(-) loss with an EC(50) = 3 microM. Diphenylamine-2-carboxylate (10(-3) M) and NPPB (10(-4) M) abolished the (125)I(-) efflux. Preincubation with 10 microM 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester or 10(-7) M thapsigargin inhibited the effect of ATP. Ionomycin (2 microM) increased (125)I(-) efflux with a time course similar to that of extracellular ATP, suggesting that the response is dependent on the intracellular Ca(2+) concentration ([Ca(2+)](i)). The ATP agonist potency order was ATP >/= UTP > ATPgammaS. Suramin (500 microM) inhibited the ATP-induced (125)I(-) efflux, consistent with P2 purinoceptors. (125)I(-) effluxes from cells grown on permeable filters suggest that ATP induced an apical efflux that was mediated via apical P2 receptors. Whole cell experiments showed that ATP (100 microM) activated outwardly rectifying Cl(-) currents in the presence of 8-cyclopentyl-1,3-dipropylxanthine, excluding the involvement of P1 receptors. Ionomycin activated Cl(-) currents similar to those developed with ATP. These results demonstrate the presence of a purinergic regulatory mechanism involving ATP, apical P2Y2 receptors, and Ca(2+) mobilization for apical Cl(-) conductance in a distal tubule cell line.
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Affiliation(s)
- I Rubera
- Unité Mixte de Recherche 6548, Centre National de la Recherche Scientifique, Université de Nice-Sophia Antipolis, 06108 Nice Cedex 2, France
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Boese SH, Glanville M, Aziz O, Gray MA, Simmons NL. Ca2+ and cAMP-activated Cl- conductances mediate Cl- secretion in a mouse renal inner medullary collecting duct cell line. J Physiol 2000; 523 Pt 2:325-38. [PMID: 10699078 PMCID: PMC2269816 DOI: 10.1111/j.1469-7793.2000.t01-1-00325.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. The nature of Cl- conductance(s) participating in transepithelial anion secretion by renal inner medullary collecting duct (IMCD, mIMCD-K2 cell line) was investigated. 2. Extracellular ATP (100 microM) stimulated a transient increase in both whole-cell Cl- conductance and intracellular free Ca2+. In contrast, ionomycin (10-100 nM) caused a sustained increase in whole-cell Cl- conductance. Pre-loading cells with the Ca2+ buffer BAPTA abolished the ATP-dependent responses and delayed the onset of the increase observed with ionomycin. 3. The Ca2+-activated whole-cell Cl- current stimulated by ATP (peak) and ionomycin (maximal) displayed (i) a linear steady-state current-voltage relationship and (ii) time and voltage dependence with slow activation at +80 mV and slow inactivation at -80 mV. In BAPTA-loaded cells, ionomycin-elicited whole-cell currents exhibited pronounced outward rectification with time-dependent activation/inactivation. 4. Ca2+-activated and forskolin-activated Cl- conductances co-exist since ATP activation of whole-cell current occurred during a maximal stimulation by forskolin in single cell recordings. 5. In IMCD epithelial layers, ATP and ionomycin stimulated an inward short circuit current (Isc) dependent upon basal medium Na+ and Cl-/HCO3- but independent of the presence of apical bathing medium Na+ and Cl-/HCO3-. This was identical to forskolin stimulation and consistent with transepithelial anion secretion. 6. PCR amplification of reverse-transcribed mRNA using gene-specific primers demonstrated expression of both cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and Ca2+-activated Cl- channel (mCLCA1) mRNA in mIMCD-K2 cells. 7. Ca2+ and forskolin-activated Cl- conductances participate in anion secretion by IMCD.
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Affiliation(s)
- S H Boese
- Department of Physiological Sciences, Medical School, Framlington Place, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK
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Mohamed A, Ferguson D, Seibert FS, Cai HM, Kartner N, Grinstein S, Riordan JR, Lukacs GL. Functional expression and apical localization of the cystic fibrosis transmembrane conductance regulator in MDCK I cells. Biochem J 1997; 322 ( Pt 1):259-65. [PMID: 9078271 PMCID: PMC1218186 DOI: 10.1042/bj3220259] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The gene product affected in cystic fibrosis, the cystic fibrosis transmembrane conductance regulator (CFTR), is a chlorideselective ion channel that is regulated by cAMP-dependent protein kinase-mediated phosphorylation, ATP binding and ATP hydrolysis. Mutations in the CFTR gene may result in cystic fibrosis characterized by severe pathology (e.g. recurrent pulmonary infection, male infertility and pancreatic insufficiency) involving organs expressing the CFTR. Interestingly, in the kidney, where expression of the CFTR has been reported, impaired ion transport in patients suffering from cystic fibrosis could not be observed. To understand the role of the CFTR in chloride transport in the kidney, we attempted to identify an epithelial cell line that can serve as a model. We demonstrate that the CFTR is expressed constitutively in Madine-Darby canine kidney (MDCK) type I cells, which are thought to have originated from the distal tubule of the dog nephron. We show expression at the mRNA level, using reverse transcriptase-PCR, and at the protein level, using Western blot analysis with three different monoclonal antibodies. Iodide efflux measurements indicate that CFTR expression confers a plasma membrane anion conductance that is responsive to stimulation by cAMP. The cAMP-stimulated iodide release is sensitive to glybenclamide, diphenylamine carboxylic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid, but not to 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid, an inhibitor profile characteristic of the CFTR chloride channel. Finally, the polarized localization of the CFTR to the apical plasma membrane was established by iodide efflux measurements and cell-surface biotinylation on MDCK I monolayers. Interestingly, MDCK type II cells, which are thought to have originated from the proximal tubule of the kidney, lack CFTR protein expression and cAMP-stimulated chloride conductance. In conclusion, we propose that MDCK type I and II cells can serve as convenient model systems to study the physiological role and differential expression of CFTR in the distal and proximal tubule respectively.
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Affiliation(s)
- A Mohamed
- Hospital for Sick Children, Research Institute, Toronto, Canada
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Guinamard R, Paulais M, Teulon J. Inhibition of a small-conductance cAMP-dependent Cl- channel in the mouse thick ascending limb at low internal pH. J Physiol 1996; 490 ( Pt 3):759-65. [PMID: 8683473 PMCID: PMC1158712 DOI: 10.1113/jphysiol.1996.sp021183] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
1. A small-conductance Cl- channel that is stimulated by ATP and protein kinase A has been identified in the basolateral membranes of cortical thick ascending limbs (CTALs) of the mouse nephron. The present study uses the cell-attached and inside-out variants of the patch-clamp technique to investigate the pH sensitivity of this channel. 2. The open-state probability (Po) was dependent upon the internal pH in inside-out patches. Expressed as a percentage of the Po value at pH 7.2, Po increased to about 180% at pH 7.6, and decreased to 25% at pH 6.8. Po was close to zero at pH 6.4. The internal pH had no effect on the channel unit conductance. 3. The effect of pH on the CTAL Cl- channel was assessed in intact cells using NH4Cl to acidify the intracellular compartment. Experiments with the pH-sensitive fluorescent dye 2',7'-(carboxyethyl)-5'(6')-carboxy fluorescein penta-acetoxymethyl ester (BCECF) indicated that 1 mmol l-1 NH4Cl acidified the cytoplasm by 0.15 pH units and 5 mmol l-1 NH4Cl by 0.34 pH units. These concentrations of NH4Cl reduced the activity of the CTAL Cl- channel by 24 and 82% in cell-attached patches, showing that moderate changes in internal pH substantially altered the activity of this channel. NH4+ had no direct effect on channel activity. 4. Inhibition at low pH is a newly discovered property of small-conductance Cl- channels in epithelia, which might help discriminate between types of Cl- channel.
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Affiliation(s)
- R Guinamard
- INSERM Unité 323, Faculté de Médecine Necker Enfants-Malades, Paris, France
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Brochiero E, Banderali U, Lindenthal S, Raschi C, Ehrenfeld J. Basolateral membrane chloride permeability of A6 cells: implication in cell volume regulation. Pflugers Arch 1995; 431:32-45. [PMID: 8584416 DOI: 10.1007/bf00374375] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The permeability to Cl- of the basolateral membrane (blm) was investigated in renal (A6) epithelial cells, assessing their role in transepithelial ion transport under steady-state conditions (isoosmotic) and following a hypoosmotic shock (i.e. in a regulatory volume decrease, RVD). Three different complementary studies were made by measuring: (1) the Cl- transport rates (delta F/Fo s-1 (x10(-3))), where F is the fluorescence of N-(6-methoxyquinoyl) acetoethyl ester, MQAE, and Fo the maximal fluorescence (x10(-3)) of both membranes by following the intracellular Cl- activities (ai Cl-, measured with MQAE) after extracellular Cl- substitution (2) the blm 86Rb and 36Cl uptakes and (3) the cellular potential and Cl- current using the whole-cell patch-clamp technique to differentiate between the different Cl- transport mechanisms. The permeability of the blm to Cl- was found to be much greater than that of the apical membranes under resting conditions: aiCl- changes were 5.3 +/- 0.7 mM and 25.5 +/- 1.05 mM (n = 79) when Cl- was substituted by NO3(-) in the media bathing apical and basolateral membranes. The Cl- transport rate of the blm was blocked by bumetanide (100 microM) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 50 microM) but not by N-phenylanthranilic acid (DPC, 100 microM). 86Rb and 36Cl uptake experiments confirmed the presence of a bumetanide- and a NPPB-sensitive Cl- pathway, the latter being approximately three times more important than the former (Na/K/2Cl cotransporter). Appli-cation of a hypoosmotic medium to the serosal side of the cell increased delta F/Fo s-1 (x10(-3)) after extracellular Cl- substitution (1.03 +/- 0.10 and 2.45 +/- 0.17 arbitrary fluorescent units s-1 for isoosmotic and hypoosmotic conditions respectively, n = 11); this delta F/Fo s-1 (x10(-3)) increase was totally blocked by serosal NPPB application; on the other hand, cotransporter activity was decreased by the hypoosmotic shock. Cellular Ca2+ depletion had no effect on delta F/Fo s-1 (x10(-3)) under isoosmotic conditions, but blocked the delta F/Fo s-1 (x10(-3)) increase induced by a hypoosmotic stress. Under isotonic conditions the measured cellular potential at rest was -37.2 +/- 4.0 mV but reached a maximal and transient depolarization of -25.1 +/- 3.7 mV (n = 9) under hypoosmotic conditions. The cellular current at a patch-clamping cellular potential of -85 mV (close to the Nernst equilibrium potential for K+) was blocked by NPPB and transiently increased by hypoosmotic shock (≈50% maximum increase). This study demonstrates that the major component of Cl- transport through the blm of the A6 monolayer is a conductive pathway (NPPB-sensitive Cl- channels) and not a Na/K/2Cl cotransporter. These channels could play a role in transepithelial Cl- absorption and cell volume regulation. The increase in the blm Cl- conductance, inducing a depolarization of these membranes, is proposed as one of the early events responsible for the stimulation of the 86Rb efflux involved in cell volume regulation.
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Affiliation(s)
- E Brochiero
- Department of Cellular and Molecular Biology, CEA-URA 1855 (CNRS), Laboratoire Jean Maetz, BP 68, F-06230 Villefranche/Mer, France
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Guinamard R, Chraïbi A, Teulon J. A small-conductance Cl- channel in the mouse thick ascending limb that is activated by ATP and protein kinase A. J Physiol 1995; 485 ( Pt 1):97-112. [PMID: 7658386 PMCID: PMC1157975 DOI: 10.1113/jphysiol.1995.sp020715] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. Chloride channels were identified in the basolateral membrane of isolated cortical thick ascending limbs (CTALs) of the mouse nephron by the patch-clamp technique. A channel with a conductance of 45 pS, previously shown to be Cl- selective, was detected in 21% of cell-attached patches when CTAL fragments were pre-incubated with 10 mumol l-4 forskolin for at least 15 min. The same channel was found in only 8.5% of cell-attached patches formed on unstimulated tubules. 2. Another channel with a smaller conductance (7-9 pS) was found in 42.8% of cell-attached patches and 57% of inside-out patches in unstimulated CTAL tubules, but in 82-87% of patches from forskolin-treated tubules. 3. The small channels was Cl- selective (Cl(-)-to-Na+ permeability ratio, PCl/PNa = 9.8) with the permeability sequence: NO3- > Br- > Cl- > F- > gluconate. Channel activity decreased (Br-) or disappeared (NO3-) at negative voltages. At 140 mmol l-1, I- completely inhibited channel activity at all voltages, but a PI/PCl ratio of 1.6 was estimated using a low I- concentration (10 mmol l-1). 4. Internal adenosine triphosphate (ATP) increased normalized current (nPo) in 48% of inside-out patches containing Cl- channels from unstimulated tubules and in 63% of patches from forskolin-treated CTAL tubules. The non-hydrolysable ATP analogue, adenosine 5'-adenylyl imidodiphosphate (AMP-PNP) did not increase channel activity. 5. Adding the catalytic subunit of protein kinase A to the bath in the presence of ATP increased the activity of the small channel in 58% of inside-out patches from unstimulated tubules, but it had no effect on the 45 pS channel. 6. The Cl- channel blockers 5-nitro-2-(3-phenylpropylamine)-benzoic acid (NPPB), 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) or glibenclamide, all at 0.1 mmol l-1, and diphenylamine-2-carboxylic acid (DPC), at 1 mmol l-1, inhibited the small channel activity by 80-100% in inside-out patches. 7. These results indicate that two Cl- channels with contrasting properties mediate the basolateral step of NaCl absorption in the thick ascending limb of the loop of Henle.
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Husted RF, Volk KA, Sigmund RD, Stokes JB. Anion secretion by the inner medullary collecting duct. Evidence for involvement of the cystic fibrosis transmembrane conductance regulator. J Clin Invest 1995; 95:644-50. [PMID: 7532187 PMCID: PMC295530 DOI: 10.1172/jci117709] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
It is well established that the terminal renal collecting duct is capable of electrogenic Na+ absorption. The present experiments examined other active ion transport processes in primary cultures of the rat inner medullary collecting duct. When the amiloride analogue benzamil inhibited electrogenic Na+ absorption, cAMP agonists stimulated a transmonolayer short circuit current that was not dependent on the presence of Na+ in the apical solution, but was dependent on the presence of Cl- and HCO3-. This current was not inhibited by the loop diuretic bumetanide, but was inhibited by ouabain, an inhibitor of the Na+/K+ pump. The current was reduced by anion transport inhibitors, with a profile similar to that seen for inhibitors of the cystic fibrosis transmembrane conductance regulator (CFATR) Cl- channel. Using several PCR strategies, we demonstrated fragments of the predicted lengths and sequence identity with the rat CFTR. Using whole-cell patch-clamp analysis, we demonstrated a cAMP-stimulated Cl- current with characteristics of the CFTR. We conclude that the rat inner medullary collecting duct has the capacity to secrete anions. It is highly likely that the CFTR Cl- channel is involved in this process.
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Affiliation(s)
- R F Husted
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242
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