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Serrano-Morillas N, González-Alayón C, Vastola-Mascolo A, Rodríguez-Rodríguez AE, Hernández G, Porrini E, Hernández-Guerra M, Alvarez de la Rosa D. Decaying kidney function during cirrhosis correlates with remodeling of distal colon aldosterone target gene expression. Am J Physiol Gastrointest Liver Physiol 2023; 325:G306-G317. [PMID: 37461846 DOI: 10.1152/ajpgi.00073.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 06/21/2023] [Accepted: 07/12/2023] [Indexed: 08/03/2023]
Abstract
Liver cirrhosis is associated to circulatory abnormalities leading to hypovolemia and stimulation of the renin-angiotensin-aldosterone system (RAAS). Advanced stages of the disease cause renal failure, impairing K+ and Na+ homeostasis. It has been proposed that the distal colon undergoes functional remodeling during renal failure, in particular by aldosterone-driven increased K+ excretion. In this study, we compared the transcriptional response of aldosterone target genes in the rat distal colon under two models of increased circulating aldosterone (one with concomitant RAAS activation) and in a model of secondary hyperaldosteronism induced by cirrhosis. The expression of a subset of these genes was also tested in distal colon biopsies from control subjects or patients with cirrhosis with varying levels of disease progression and treated or not with mineralocorticoid receptor inhibitor spironolactone. We examined known aldosterone-regulated transcripts involved in corticosteroid signaling and transepithelial ion transport. In addition, we included aldosterone-regulated genes related to cell proliferation. Our comparison revealed multiple aldosterone target genes upregulated in the rat distal colon during decompensated cirrhosis. Epithelial Na+ channel β and γ subunit expression correlated positively with plasma aldosterone concentration and negatively with glomerular filtration rate. Patients with cirrhosis showed increased expression of 11-β-hydroxysteroid-dehydrogenase 2 (11βHSD2), which was reverted by spironolactone treatment, suggesting a sensitization of the distal colon to aldosterone action. In summary, our data show that decaying kidney function during cirrhosis progression toward a decompensated state with hypovolemia correlates with remodeling of distal colon ion transporter expression, supporting a role for aldosterone in the process.NEW & NOTEWORTHY Liver cirrhosis progression significantly alters ion transporter subunit expression in the rat distal colon, a change that correlated well with declining kidney function and the severity of the disease. Our data suggest that the steroid hormone aldosterone participates in this homeostatic response to maintain electrolyte balance.
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Affiliation(s)
- Natalia Serrano-Morillas
- Departamento de Ciencias Médicas Básicas, Universidad de La Laguna, La Laguna, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
| | | | - Arianna Vastola-Mascolo
- Departamento de Ciencias Médicas Básicas, Universidad de La Laguna, La Laguna, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
| | - Ana E Rodríguez-Rodríguez
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
- Research Unit, Hospital Universitario de Canarias, La Laguna, Spain
| | - Guadalberto Hernández
- Departamento de Ciencias Médicas Básicas, Universidad de La Laguna, La Laguna, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
| | - Esteban Porrini
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
- Research Unit, Hospital Universitario de Canarias, La Laguna, Spain
| | - Manuel Hernández-Guerra
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
- Research Unit, Hospital Universitario de Canarias, La Laguna, Spain
- Servicio de Aparato Digestivo, Hospital Universitario de Canarias, La Laguna, Spain
| | - Diego Alvarez de la Rosa
- Departamento de Ciencias Médicas Básicas, Universidad de La Laguna, La Laguna, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, La Laguna, Spain
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2
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Rossier BC, Baker ME, Studer RA. Epithelial sodium transport and its control by aldosterone: the story of our internal environment revisited. Physiol Rev 2015; 95:297-340. [PMID: 25540145 DOI: 10.1152/physrev.00011.2014] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transcription and translation require a high concentration of potassium across the entire tree of life. The conservation of a high intracellular potassium was an absolute requirement for the evolution of life on Earth. This was achieved by the interplay of P- and V-ATPases that can set up electrochemical gradients across the cell membrane, an energetically costly process requiring the synthesis of ATP by F-ATPases. In animals, the control of an extracellular compartment was achieved by the emergence of multicellular organisms able to produce tight epithelial barriers creating a stable extracellular milieu. Finally, the adaptation to a terrestrian environment was achieved by the evolution of distinct regulatory pathways allowing salt and water conservation. In this review we emphasize the critical and dual role of Na(+)-K(+)-ATPase in the control of the ionic composition of the extracellular fluid and the renin-angiotensin-aldosterone system (RAAS) in salt and water conservation in vertebrates. The action of aldosterone on transepithelial sodium transport by activation of the epithelial sodium channel (ENaC) at the apical membrane and that of Na(+)-K(+)-ATPase at the basolateral membrane may have evolved in lungfish before the emergence of tetrapods. Finally, we discuss the implication of RAAS in the origin of the present pandemia of hypertension and its associated cardiovascular diseases.
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Affiliation(s)
- Bernard C Rossier
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland; Division of Nephrology-Hypertension, University of California San Diego, La Jolla, California; and Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
| | - Michael E Baker
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland; Division of Nephrology-Hypertension, University of California San Diego, La Jolla, California; and Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
| | - Romain A Studer
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland; Division of Nephrology-Hypertension, University of California San Diego, La Jolla, California; and Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
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3
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Ziera T, Irlbacher H, Fromm A, Latouche C, Krug SM, Fromm M, Jaisser F, Borden SA. Cnksr3 is a direct mineralocorticoid receptor target gene and plays a key role in the regulation of the epithelial sodium channel. FASEB J 2009; 23:3936-46. [PMID: 19567370 DOI: 10.1096/fj.09-134759] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Aldosterone is the principal hormonal regulator of sodium homeostasis in vertebrates. It exerts its actions through the mineralocorticoid receptor (MR) that regulates the transcription of specific target genes. In recent years, a number of MR target genes have been identified that are involved in the regulation of the epithelial sodium channel (ENaC), a key modulator of renal sodium absorption. Here we report the identification of cnksr3 as a direct MR target gene that is up-regulated in response to physiological concentrations of aldosterone. The cnksr3 promoter exhibits two functional aldosterone-responsive regions, which were bound by the MR as assessed by chromatin immunoprecipitation (ChIP). In vivo, CNKSR3 was highly expressed in the renal cortical collecting duct (CCD), the prime target segment of aldosterone-regulated sodium retention in the kidney. CCD cell lines stably overexpressing or silencing CNKSR3 were electrophysiologically analyzed and show that CNKSR3 expression correlated with and is required for ENaC-mediated transepithelial sodium transport. In parallel, CNKSR3 expression led to decreased MEK phosphorylation. We conclude that CNKSR3, a homologue of scaffold proteins involved in MAPK pathway regulation, is a direct target of MR and is required for the maintenance of transepithelial sodium transport in the kidney.
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Affiliation(s)
- Tim Ziera
- Therapeutic Research Women's Health, Bayer Schering Pharma AG, Müllerstr. 178, 13353 Berlin, Germany
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4
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Bertog M, Cuffe JE, Pradervand S, Hummler E, Hartner A, Porst M, Hilgers KF, Rossier BC, Korbmacher C. Aldosterone responsiveness of the epithelial sodium channel (ENaC) in colon is increased in a mouse model for Liddle's syndrome. J Physiol 2007; 586:459-75. [PMID: 18006588 DOI: 10.1113/jphysiol.2007.140459] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Liddle's syndrome is an autosomal dominant form of human hypertension, caused by gain-of-function mutations of the epithelial sodium channel (ENaC) which is expressed in aldosterone target tissues including the distal colon. We used a mouse model for Liddle's syndrome to investigate ENaC-mediated Na+ transport in late distal colon by measuring the amiloride-sensitive transepithelial short circuit current (Delta I SC-Ami) ex vivo. In Liddle mice maintained on a standard salt diet, Delta I SC-Ami was only slightly increased but plasma aldosterone (P Aldo) was severely suppressed. Liddle mice responded to a low or a high salt diet by increasing or decreasing, respectively, their P Aldo and Delta I SC-Ami. However, less aldosterone was required in Liddle animals to achieve similar or even higher Na+ transport rates than wild-type animals. Indeed, the ability of aldosterone to stimulate Delta I SC-Ami was about threefold higher in Liddle animals than in the wild-type controls. Application of aldosterone to colon tissue in vitro confirmed that ENaC stimulation by aldosterone was not only preserved but enhanced in Liddle mice. Aldosterone-induced transcriptional up-regulation of the channel's beta- and gamma-subunit (beta ENaC and gamma ENaC) and of the serum- and glucocorticoid-inducible kinase 1 (SGK1) was similar in colon tissue from Liddle and wild-type animals, while aldosterone had no transcriptional effect on the alpha-subunit (alpha ENaC). Moreover, Na+ feedback regulation was largely preserved in colon tissue of Liddle animals. In conclusion, we have demonstrated that in the colon of Liddle mice, ENaC-mediated Na+ transport is enhanced with an increased responsiveness to aldosterone. This may be pathophysiologically relevant in patients with Liddle's syndrome, in particular on a high salt diet, when suppression of P Aldo is likely to be insufficient to reduce Na+ absorption to an appropriate level.
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Affiliation(s)
- Marko Bertog
- Institut für Zelluläre und Molekulare Physiologie, Waldstr. 6, 91054 Erlangen, Germany
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5
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Barmeyer C, Amasheh S, Tavalali S, Mankertz J, Zeitz M, Fromm M, Schulzke JD. IL-1beta and TNFalpha regulate sodium absorption in rat distal colon. Biochem Biophys Res Commun 2004; 317:500-7. [PMID: 15063785 DOI: 10.1016/j.bbrc.2004.03.072] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Indexed: 11/30/2022]
Abstract
The epithelial Na+ channel (ENaC) provides the main absorptive pathway of the distal large intestine. This study aimed to characterize regulatory influences of cytokines in rat late distal colon. After 6 h incubation with either IL1beta, TNFalpha, IFNgamma, or combinations of TNFalpha and IFNgamma, ENaC was measured as electrogenic Na+ transport after 8 h induction by 3 nM aldosterone (JNa) in totally stripped specimens in the Ussing chamber. Subsequently, alpha-, beta-, and gamma-ENaC subunit mRNAs were analyzed by Northern blotting. The gamma-ENaC promoter was cloned and characterized by reporter gene assays. IL-1beta and TNFalpha, but not interferon-gamma, decreased JNa. In parallel, beta- and gamma-ENaC transcription was inhibited, whereas alpha-ENaC was unaffected. gamma-ENaC promoter activity was inhibited by IL-1beta and TNFalpha but not by IFNgamma. We conclude that the pro-inflammatory cytokines IL-1beta and TNFalpha inhibit electrogenic sodium absorption in rat distal colon by mRNA expression regulation of the beta- and gamma-ENaC subunits.
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Affiliation(s)
- Christian Barmeyer
- Department of Gastroenterology, Infectious Diseases and Rheumatology, Campus Benjamin Franklin, Charité University Medicine Berlin, 12200 Berlin, Germany
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6
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Vidyasagar S, Rajendran VM, Binder HJ. Three distinct mechanisms of HCO3- secretion in rat distal colon. Am J Physiol Cell Physiol 2004; 287:C612-21. [PMID: 15308466 DOI: 10.1152/ajpcell.00474.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
HCO(3)(-) secretion has long been recognized in the mammalian colon, but it has not been well characterized. Although most studies of colonic HCO(3)(-) secretion have revealed evidence of lumen Cl(-) dependence, suggesting a role for apical membrane Cl(-)/HCO(3)(-) exchange, direct examination of HCO(3)(-) secretion in isolated crypt from rat distal colon did not identify Cl(-)-dependent HCO(3)(-) secretion but did reveal cAMP-induced, Cl(-)-independent HCO(3)(-) secretion. Studies were therefore initiated to determine the characteristics of HCO(3)(-) secretion in isolated colonic mucosa to identify HCO(3)(-) secretion in both surface and crypt cells. HCO(3)(-) secretion was measured in rat distal colonic mucosa stripped of muscular and serosal layers by using a pH stat technique. Basal HCO(3)(-) secretion (5.6 +/- 0.03 microeq.h(-1).cm(-2)) was abolished by removal of either lumen Cl(-) or bath HCO(3)(-); this Cl(-)-dependent HCO(3)(-) secretion was also inhibited by 100 microM DIDS (0.5 +/- 0.03 microeq.h(-1).cm(-2)) but not by 5-nitro-3-(3-phenylpropyl-amino)benzoic acid (NPPB), a Cl(-) channel blocker. 8-Bromo-cAMP induced Cl(-)-independent HCO(3)(-) secretion (and also inhibited Cl(-)-dependent HCO(3)(-) secretion), which was inhibited by NPPB and by glibenclamide, a CFTR blocker, but not by DIDS. Isobutyrate, a poorly metabolized short-chain fatty acid (SCFA), also induced a Cl(-)-independent, DIDS-insensitive, saturable HCO(3)(-) secretion that was not inhibited by NPPB. Three distinct HCO(3)(-) secretory mechanisms were identified: 1) Cl(-)-dependent secretion associated with apical membrane Cl(-)/HCO(3)(-) exchange, 2) cAMP-induced secretion that was a result of an apical membrane anion channel, and 3) SCFA-dependent secretion associated with an apical membrane SCFA/HCO(3)(-) exchange.
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Affiliation(s)
- Sadasivan Vidyasagar
- Dept. of Internal Medicine, Yale University, PO Box 208019, New Haven, CT 06520, USA
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7
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Inagaki A, Yamaguchi S, Ishikawa T. Amiloride-sensitive epithelial Na+channel currents in surface cells of rat rectal colon. Am J Physiol Cell Physiol 2004; 286:C380-90. [PMID: 14576089 DOI: 10.1152/ajpcell.00373.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Surface cells of the mammalian distal colon are shown to molecularly express the amiloride-sensitive epithelial Na+channel composed of three homologous subunits (α-, β-, and γ-ENaC). However, because basic electrophysiological properties of amiloride-sensitive Na+channels expressed in these cells are largely unknown at the cellular level, functional evidence for the involvement of the subunits in the native channels is incomplete. Using electrophysiological techniques, we have now characterized functional properties of native ENaC in surface cells of rectal colon (RC) of rats fed a normal Na+diet. Ussing chamber experiments showed that apical amiloride inhibited a basal short-circuit current in mucosal preparation of RC with an apparent half-inhibition constant ( Ki) value of 0.20 μM. RT-PCR analysis confirmed the presence of transcripts of α-, β-, and γ-rENaC in rectal mucosa. Whole cell patch-clamp experiments in surface cells of intact crypts acutely isolated from rectal mucosa identified an inward cationic current, which was inhibited by amiloride with a Kivalue of 0.12 μM at a membrane potential of –64 mV, the inhibition being weakly voltage dependent. Conductance ratios of the currents were Li+(1.8) > Na+(1) >> K+(≈0), respectively. Amiloride-sensitive current amplitude was almost the same at 15 or 150 mM extracellular Na+, suggesting a high Na+affinity for current activation. These results are consistent with the hypothesis that a heterooligomer composed of α-, β-, and γ-ENaC may be the molecular basis of the native channels, which are responsible for amiloride-sensitive electrogenic Na+absorption in rat rectal colon.
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Affiliation(s)
- A Inagaki
- Laboratory of Physiology, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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8
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Barmeyer C, Harren M, Schmitz H, Heinzel-Pleines U, Mankertz J, Seidler U, Horak I, Wiedenmann B, Fromm M, Schulzke JD. Mechanisms of diarrhea in the interleukin-2-deficient mouse model of colonic inflammation. Am J Physiol Gastrointest Liver Physiol 2004; 286:G244-52. [PMID: 14715519 DOI: 10.1152/ajpgi.00141.2003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Colitis in interleukin-2-deficient (IL-2(-/-)) mice resembles ulcerative colitis in humans. We studied epithelial transport and barrier function in IL-2(-/-) mice and used this model to characterize mechanisms of diarrhea during intestinal inflammation. (22)Na(+) and (36)Cl(-) fluxes were measured in proximal colon. Net Na(+) flux was reduced from 4.0 +/- 0.5 to 0.8 +/- 0.5 micromol.h(-1).cm(-2), which was paralleled by diminished mRNA and protein expression of the Na(+)/H(+) exchanger NHE3. Net Cl(-) flux was also decreased from 2.2 +/- 1.6 to -2.7 +/- 0.6 micromol.h(-1).cm(-2), indicating impaired Na(+)-Cl(-) absorption. In distal colon, aldosterone-induced electrogenic Na(+) absorption was 6.1 +/- 0.9 micromol.h(-1).cm(-2) in controls and was abolished in IL-2(-/-) mice. Concomitantly, mRNA expression of beta- and gamma-subunits of the epithelial sodium channel (ENaC) was reduced. Epithelial barrier was studied in proximal colon by impedance technique and mannitol fluxes. In contrast to ulcerative colitis, epithelial resistance was increased and mannitol fluxes were decreased in IL-2(-/-) mice. This was in accord with the findings of reduced ion transport as well as increased expression of tight junction proteins occludin and claudin-1, -2, -3, and -5. In conclusion, the IL-2(-/-) mucosa exhibits impaired electroneutral Na(+)-Cl(-) absorption and electrogenic Na(+) transport due to reduced mRNA and protein expression of NHE3 and ENaC beta- and gamma-subunit mRNA. This represents a model of early intestinal inflammation with absorptive dysfunction due to impaired transport protein expression/function while epithelial barrier is still intact. Therefore, this model is ideal to study regulation of transporter expression independent of barrier defects.
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Affiliation(s)
- C Barmeyer
- Department of Gastroenterology, Charité-University Medicine Berlin, 12200 Berlin, Germany
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9
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Vidyasagar S, Ramakrishna BS. Effects of butyrate on active sodium and chloride transport in rat and rabbit distal colon. J Physiol 2002; 539:163-73. [PMID: 11850510 PMCID: PMC2290116 DOI: 10.1113/jphysiol.2001.013056] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Short chain fatty acids, particularly butyrate, stimulate electroneutral NaCl absorption from the colon. Their effect in colonic epithelia lacking basal electroneutral NaCl absorption is unknown. Butyrate is also reported to inhibit active Cl- secretion in the colon. The present studies were undertaken to investigate the inter-relationships between the effects of butyrate on active Na+ and Cl- transport in the colon. Studies were carried out in rabbit distal colon (known to have predominant electrogenic Na+ absorption), rat distal colon (characterised by electroneutral Na+ absorption), and hyperaldosteronaemic rat distal colon (characterised by electrogenic Na+ absorption). The effect of cholera toxin (CT) was also noted. Potential difference, short-circuit current (I(SC)) and fluxes of Na+ and Cl- were measured in stripped mucosa under voltage-clamp conditions. Butyrate stimulated electroneutral Na+ and Cl- absorption in distal colon of normal and salt-depleted rats, and stimulated Na+ absorption in rabbit distal colon. Amiloride (10(-4) M) or CT did not inhibit this process. In rabbit distal colon, stimulation of Na+ absorption by butyrate was not dependent on the presence of Cl- in the medium. Butyrate significantly decreased conductance, decreased flux of sodium from serosa to mucosa (particularly in rabbit distal colon), and decreased I(SC). Net Cl- secretion, induced by CT, was completely inhibited by butyrate. Stimulation of Na+ absorption was independent of exposure to CT. Bumetanide reversed net Cl- secretion to net absorption, but did not alter Na+ or Cl- fluxes in tissues exposed to butyrate. Thus butyrate stimulates active Na+ absorption in colonic epithelia, with or without expression of basal Na+-H+ exchange. Independently, butyrate inhibits active Cl- secretion induced by cAMP in these epithelia.
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Affiliation(s)
- S Vidyasagar
- Department of Gastrointestinal Sciences, Christian Medical College & Hospital, Vellore 632004, India
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10
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Cuffe JE, Bertog M, Velázquez-Rocha S, Dery O, Bunnett N, Korbmacher C. Basolateral PAR-2 receptors mediate KCl secretion and inhibition of Na+ absorption in the mouse distal colon. J Physiol 2002; 539:209-22. [PMID: 11850514 PMCID: PMC2290120 DOI: 10.1113/jphysiol.2001.013159] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Proteinase-activated receptor-2 (PAR-2) may participate in epithelial ion transport regulation. Here we examined the effect of mouse activating peptide (mAP), a specific activator of PAR-2, on electrogenic transport of mouse distal colon using short-circuit current (I(SC)) measurements. Under steady-state conditions, apical application of amiloride (100 microM) revealed a positive I(SC) component of 74.3 +/- 6.8 microA x cm(-2) indicating the presence of Na+ absorption, while apical Ba2+ (10 mM) identified a negative I(SC) component of 26.2 +/- 1.8 microA x cm(-2) consistent with K+ secretion. Baseline Cl- secretion was minimal. Basolateral addition of 20 microM mAP produced a biphasic I(SC) response with an initial transient peak increase of 11.2 +/- 0.9 microA x cm(-2), followed by a sustained fall to a level 31.2 +/- 2.6 microA x cm(-2) (n = 43) below resting I(SC). The peak response was due to Cl- secretion as it was preserved in the presence of amiloride but was largely reduced in the presence of basolateral bumetanide (20 microM) or in the absence of extracellular Cl-. The secondary decline of I(SC) was also attenuated by bumetanide and by Ba2+, indicating that it is partly due to a stimulation of K+ secretion. In addition, the amiloride-sensitive I(SC) was slightly reduced by mAP, suggesting that inhibition of Na+ absorption also contributes to the I(SC) decline. Expression of PAR-2 in mouse distal colon was confirmed using RT-PCR and immunocytochemistry. We conclude that functional basolateral PAR-2 is present in mouse distal colon and that its activation stimulates Cl- and K+ secretion while inhibiting baseline Na+ absorption.
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Affiliation(s)
- John E Cuffe
- University Laboratory of Physiology, Oxford University, Parks Road, Oxford, OX1 3PT, UK
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11
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Epple HJ, Amasheh S, Mankertz J, Goltz M, Schulzke JD, Fromm M. Early aldosterone effect in distal colon by transcriptional regulation of ENaC subunits. Am J Physiol Gastrointest Liver Physiol 2000; 278:G718-24. [PMID: 10801264 DOI: 10.1152/ajpgi.2000.278.5.g718] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Aldosterone-induced sodium absorption is mediated by the epithelial Na(+) channel (ENaC). It is thought that the "early effect" is not based on genomic regulation of ENaC expression, because ENaC subunit transcription was reported to start later than Na(+) transport. We investigated electrogenic Na(+) absorption (J(Na)) and, in identical tissues, mRNA expression of ENaC subunits in early (EDC) and late (LDC) distal colon of the rat. In both segments, 8-h in vitro incubation with 3 nM aldosterone enhanced expression of beta- and gamma-ENaC mRNA and induced J(Na). J(Na) was 10 times higher in LDC than in EDC. alpha-ENaC mRNA was unchanged in EDC, whereas it decreased in LDC. In LDC, beta- and gamma-ENaC mRNA was induced 1 h after aldosterone addition, whereas J(Na) became apparent >1 h later. Downregulation of alpha-ENaC mRNA did not take part in acute regulation because it started after a lag time of 3 h. Time correlation of beta- and gamma-ENaC induction and J(Na) stimulation suggests that the early aldosterone effect on Na(+) absorption in distal colon is caused by transcriptional upregulation of beta- and gamma-ENaC expression.
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Affiliation(s)
- H J Epple
- Department of Clinical Physiology, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, 12200 Berlin, Germany
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12
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Horisberger JD. Chapter 11 Electrogenic transepithelial Na+ transport in the colon. CURRENT TOPICS IN MEMBRANES 2000. [DOI: 10.1016/s1063-5823(00)50013-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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Grotjohann I, Gitter AH, Köckerling A, Bertog M, Schulzke JD, Fromm M. Localization of cAMP- and aldosterone-induced K+ secretion in rat distal colon by conductance scanning. J Physiol 1998; 507 ( Pt 2):561-70. [PMID: 9518713 PMCID: PMC2230785 DOI: 10.1111/j.1469-7793.1998.561bt.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. Aldosterone- and adrenaline-induced K+ secretion were investigated in rat late distal colon using conductance scanning and Ussing chamber techniques. K+ secretion was unmasked by the K+ channel blocker tetraethylammonium (TEA). Electrogenic Na+ absorption was inhibited by amiloride. Rb+ net fluxes consistently measured about 80% of K+ secretion estimated using change in short-circuit current (delta ISC) measurements. 2. Partial block of K+ absorption by mucosal ouabain did not change TEA-sensitive K+ secretion. Thus, K+ absorption and K+ secretion are not coupled. 3. Additivity of Rb+ fluxes as well as delta ISC caused by 3 nM aldosterone (6 h in vitro incubation) and, subsequently, adrenaline suggested additivity of aldosterone-induced and cAMP-mediated K+ secretion in the presence of amiloride. 4. Conductance scanning under control conditions revealed a small TEA-sensitive K+ conductivity in surface epithelium (0.3 +/- 0.2 mS cm-2) but not in crypts, as well as a small basal K+ secretion in surface epithelium (delta ISC = 0.3 mumol h-1 cm-2), which increased during sham incubation. 5. Aldosterone (3 nM, 6 h in vitro incubation) resulted, after correction for the basal K+ secretion, in a K+ secretion of delta ISC = 0.9 mumol h-1 cm-2. Aldosterone induced a TEA-sensitive conductivity of 1.1 +/- 0.3 mS cm-2 in surface epithelium, but not in crypts. 6. Adrenaline (5 microM) caused, in fresh tissue, a K+ secretion of delta ISC = 1.2 mumol h-1 cm-2 and equal conductivity changes in crypts (0.7 +/- 0.2 mS cm-2) and surface epithelium (0.7 +/- 0.1 mS cm-2). 7. We conclude that K+ secretion induced by aldosterone in physiological concentration is restricted to surface epithelium, whereas cAMP-mediated K+ secretion is located equally in crypts and surface epithelium.
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Affiliation(s)
- I Grotjohann
- Institut für Klinische Physiologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Germany
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14
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Verrey F. Transcriptional control of sodium transport in tight epithelial by adrenal steroids. J Membr Biol 1995; 144:93-110. [PMID: 7595948 DOI: 10.1007/bf00232796] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- F Verrey
- Institute of Physiology, University of Zurich, Switzerland
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