TY - JOUR
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 - LaRusso, Nicholas F.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1997/5
Y1 - 1997/5
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.
KW - Biliary epithelia
KW - Carrier proteins
KW - Liver
KW - Monosaccharide
KW - Polarized primary cultures
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U2 - 10.1152/ajpgi.1997.272.5.g1168
DO - 10.1152/ajpgi.1997.272.5.g1168
M3 - Article
C2 - 9176227
AN - SCOPUS:0030918556
SN - 0193-1857
VL - 272
SP - G1168-G1174
JO - American Journal of Physiology - Gastrointestinal and Liver Physiology
JF - American Journal of Physiology - Gastrointestinal and Liver Physiology
IS - 5 35-5
ER -