Kinetic and molecular identification of sodium-dependent glucose transporter in normal rat cholangiocytes

Konstantinos N Lazaridis, Linh Pham, Ben Vroman, Piet C. De Groen, Nicholas F La Russo

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Abstract

While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl α-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (≤90%) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na+-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na+-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume272
Issue number5 35-5
StatePublished - May 1997

Fingerprint

Sodium-Glucose Transport Proteins
Monosaccharides
Reverse Transcriptase Polymerase Chain Reaction
Glucose
Bile
Epithelium
Phlorhizin
Transcytosis
Facilitative Glucose Transport Proteins
Liver
Frozen Sections
Sucrose
Hepatocytes
Cell Membrane
Antibodies

Keywords

  • Biliary epithelia
  • Carrier proteins
  • Liver
  • Monosaccharide
  • Polarized primary cultures

ASJC Scopus subject areas

  • Gastroenterology
  • Physiology
  • Physiology (medical)

Cite this

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title = "Kinetic and molecular identification of sodium-dependent glucose transporter in normal rat cholangiocytes",
abstract = "While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl α-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (≤90{\%}) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na+-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na+-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.",
keywords = "Biliary epithelia, Carrier proteins, Liver, Monosaccharide, Polarized primary cultures",
author = "Lazaridis, {Konstantinos N} and Linh Pham and Ben Vroman and {De Groen}, {Piet C.} and {La Russo}, {Nicholas F}",
year = "1997",
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journal = "American Journal of Physiology - Renal Fluid and Electrolyte Physiology",
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T1 - Kinetic and molecular identification of sodium-dependent glucose transporter in normal rat cholangiocytes

AU - Lazaridis, Konstantinos N

AU - Pham, Linh

AU - Vroman, Ben

AU - De Groen, Piet C.

AU - La Russo, Nicholas F

PY - 1997/5

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N2 - While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl α-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (≤90%) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na+-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na+-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.

AB - While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl α-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (≤90%) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na+-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na+-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.

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KW - Carrier proteins

KW - Liver

KW - Monosaccharide

KW - Polarized primary cultures

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