Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line

Carlo Spirlì, Anna Granato, Àkos Zsembery, Franca Anglani, Lajos Okolicsànyi, Nicholas F La Russo, Gaetano Crepaldi, Mario Strazzabosco

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+ exchange (NHE) and Cl-/HCO3/- exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT- PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pH(i)) was measured by 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein microfluorometry. In HCO3-/CO2 free medium and in the presence of apical amiloride, pHi recovery from an acid load was Na+ dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+ readmission induced a slow pHi recovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pH(i) experiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume275
Issue number6 38-6
StatePublished - 1998

Fingerprint

Chloride-Bicarbonate Antiporters
Amiloride
Protein Isoforms
Cell Line
Membranes
Cytophotometry
Intrahepatic Bile Ducts
Gene Expression
Messenger RNA
Acids
Bile
Electrolytes
Perfusion
Polymerase Chain Reaction
Genes

Keywords

  • Intracellular pH
  • Reverse transcription-polymerase chain reaction

ASJC Scopus subject areas

  • Gastroenterology
  • Physiology
  • Physiology (medical)

Cite this

Spirlì, C., Granato, A., Zsembery, À., Anglani, F., Okolicsànyi, L., La Russo, N. F., ... Strazzabosco, M. (1998). Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line. American Journal of Physiology - Gastrointestinal and Liver Physiology, 275(6 38-6).

Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line. / Spirlì, Carlo; Granato, Anna; Zsembery, Àkos; Anglani, Franca; Okolicsànyi, Lajos; La Russo, Nicholas F; Crepaldi, Gaetano; Strazzabosco, Mario.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 275, No. 6 38-6, 1998.

Research output: Contribution to journalArticle

Spirlì, C, Granato, A, Zsembery, À, Anglani, F, Okolicsànyi, L, La Russo, NF, Crepaldi, G & Strazzabosco, M 1998, 'Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line', American Journal of Physiology - Gastrointestinal and Liver Physiology, vol. 275, no. 6 38-6.
Spirlì, Carlo ; Granato, Anna ; Zsembery, Àkos ; Anglani, Franca ; Okolicsànyi, Lajos ; La Russo, Nicholas F ; Crepaldi, Gaetano ; Strazzabosco, Mario. / Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line. In: American Journal of Physiology - Gastrointestinal and Liver Physiology. 1998 ; Vol. 275, No. 6 38-6.
@article{d61c3449e59d4407a2576f3e81cb415b,
title = "Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line",
abstract = "Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+ exchange (NHE) and Cl-/HCO3/- exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT- PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pH(i)) was measured by 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein microfluorometry. In HCO3-/CO2 free medium and in the presence of apical amiloride, pHi recovery from an acid load was Na+ dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+ readmission induced a slow pHi recovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pH(i) experiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.",
keywords = "Intracellular pH, Reverse transcription-polymerase chain reaction",
author = "Carlo Spirl{\`i} and Anna Granato and {\`A}kos Zsembery and Franca Anglani and Lajos Okolics{\`a}nyi and {La Russo}, {Nicholas F} and Gaetano Crepaldi and Mario Strazzabosco",
year = "1998",
language = "English (US)",
volume = "275",
journal = "American Journal of Physiology - Renal Fluid and Electrolyte Physiology",
issn = "1931-857X",
publisher = "American Physiological Society",
number = "6 38-6",

}

TY - JOUR

T1 - Functional polarity of Na+/H+ and Cl-/HCO3/- exchangers in a rat cholangiocyte cell line

AU - Spirlì, Carlo

AU - Granato, Anna

AU - Zsembery, Àkos

AU - Anglani, Franca

AU - Okolicsànyi, Lajos

AU - La Russo, Nicholas F

AU - Crepaldi, Gaetano

AU - Strazzabosco, Mario

PY - 1998

Y1 - 1998

N2 - Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+ exchange (NHE) and Cl-/HCO3/- exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT- PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pH(i)) was measured by 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein microfluorometry. In HCO3-/CO2 free medium and in the presence of apical amiloride, pHi recovery from an acid load was Na+ dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+ readmission induced a slow pHi recovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pH(i) experiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.

AB - Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+ exchange (NHE) and Cl-/HCO3/- exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT- PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pH(i)) was measured by 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein microfluorometry. In HCO3-/CO2 free medium and in the presence of apical amiloride, pHi recovery from an acid load was Na+ dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+ readmission induced a slow pHi recovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pH(i) experiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.

KW - Intracellular pH

KW - Reverse transcription-polymerase chain reaction

UR - http://www.scopus.com/inward/record.url?scp=0032416170&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032416170&partnerID=8YFLogxK

M3 - Article

C2 - 9843758

AN - SCOPUS:0032416170

VL - 275

JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology

JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology

SN - 1931-857X

IS - 6 38-6

ER -