Expression and hepatobiliary transport characteristics of the concentrative and equilibrative nucleoside transporters in sandwich-cultured human hepatocytes

Rajgopal Govindarajan, Christopher J. Endres, Dale Whittington, Edward LeCluyse, Marçal Pastor-Anglada, Chung Ming Tse, Jashvant D. Unadkat

Research output: Contribution to journalArticle

Abstract

We previously reported that both the concentrative (hCNT) and equilibrative (hENT) nucleoside transporters are expressed in the human liver (21). Here we report a study that investigated the expression of these transporters (transcripts and proteins) and their role in the hepatobiliary transport of nucleosides/nucleoside drugs using sandwich-cultured human hepatocytes. In the hepatic tissue, the rank order of the mRNA expression of the transporters was hCNT1 ≈ hENT1 > hENT2 ≈ hCNT2 > hCNT3. In sandwich-cultured hepatocytes, the mRNA expression of hCNT2 and hENT2 was comparable to that in hepatic tissue, whereas the expression of corresponding transporters in the two-dimensional hepatocyte cultures was lower. Colocalization studies demonstrated predominant localization of these transporters at the sinusoidal membrane and of hENT1, hCNT1, and hCNT2 at the canalicular membrane. In the sandwich-cultured hepatocytes, ENTs were the major contributors to the transport of thymidine (hENT1, 63%; hENT2, 23%) or guanosine (hENT1, 53%; hENT2, 24%) into the hepatocytes followed by hCNT1 (10%) for thymidine or hCNT2 (23%) for guanosine. Although ribavirin was predominately transported (89%) into the hepatocytes by hENT1, fialuridine (FIAU) was transported by both hENT1 (30%) and hCNTs (61%). The extensively metabolized natural nucleosides were not effluxed into the bile, whereas significant biliary-efflux was observed of FIAU (19%), ribavirin (30%), and formycin B (35%). We conclude that the hepatic activity of hENT1 and hCNT1/2 transporters will determine the in vivo hepatic distribution and therefore the efficacy and/or toxicity of nucleoside drugs used to treat hepatic diseases.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume295
Issue number3
DOIs
StatePublished - Sep 2008

Fingerprint

Nucleoside Transport Proteins
Hepatocytes
Nucleosides
Liver
Guanosine
Ribavirin
Thymidine
Messenger RNA
Membranes
Drug-Related Side Effects and Adverse Reactions
Bile
Pharmaceutical Preparations

Keywords

  • Biliary efflux
  • Biliary excretion
  • Hepatic diseases
  • Human concentrative nucleoside transporters
  • Human equilibrative nucleoside transporters
  • Localization
  • mRNA
  • Nucleoside drugs
  • Phosphorylation
  • Protein expression

ASJC Scopus subject areas

  • Gastroenterology
  • Physiology (medical)
  • Physiology
  • Hepatology

Cite this

Expression and hepatobiliary transport characteristics of the concentrative and equilibrative nucleoside transporters in sandwich-cultured human hepatocytes. / Govindarajan, Rajgopal; Endres, Christopher J.; Whittington, Dale; LeCluyse, Edward; Pastor-Anglada, Marçal; Tse, Chung Ming; Unadkat, Jashvant D.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 295, No. 3, 09.2008.

Research output: Contribution to journalArticle

Govindarajan, Rajgopal ; Endres, Christopher J. ; Whittington, Dale ; LeCluyse, Edward ; Pastor-Anglada, Marçal ; Tse, Chung Ming ; Unadkat, Jashvant D. / Expression and hepatobiliary transport characteristics of the concentrative and equilibrative nucleoside transporters in sandwich-cultured human hepatocytes. In: American Journal of Physiology - Gastrointestinal and Liver Physiology. 2008 ; Vol. 295, No. 3.
@article{2fab844f439a42119f4884faf9643d02,
title = "Expression and hepatobiliary transport characteristics of the concentrative and equilibrative nucleoside transporters in sandwich-cultured human hepatocytes",
abstract = "We previously reported that both the concentrative (hCNT) and equilibrative (hENT) nucleoside transporters are expressed in the human liver (21). Here we report a study that investigated the expression of these transporters (transcripts and proteins) and their role in the hepatobiliary transport of nucleosides/nucleoside drugs using sandwich-cultured human hepatocytes. In the hepatic tissue, the rank order of the mRNA expression of the transporters was hCNT1 ≈ hENT1 > hENT2 ≈ hCNT2 > hCNT3. In sandwich-cultured hepatocytes, the mRNA expression of hCNT2 and hENT2 was comparable to that in hepatic tissue, whereas the expression of corresponding transporters in the two-dimensional hepatocyte cultures was lower. Colocalization studies demonstrated predominant localization of these transporters at the sinusoidal membrane and of hENT1, hCNT1, and hCNT2 at the canalicular membrane. In the sandwich-cultured hepatocytes, ENTs were the major contributors to the transport of thymidine (hENT1, 63{\%}; hENT2, 23{\%}) or guanosine (hENT1, 53{\%}; hENT2, 24{\%}) into the hepatocytes followed by hCNT1 (10{\%}) for thymidine or hCNT2 (23{\%}) for guanosine. Although ribavirin was predominately transported (89{\%}) into the hepatocytes by hENT1, fialuridine (FIAU) was transported by both hENT1 (30{\%}) and hCNTs (61{\%}). The extensively metabolized natural nucleosides were not effluxed into the bile, whereas significant biliary-efflux was observed of FIAU (19{\%}), ribavirin (30{\%}), and formycin B (35{\%}). We conclude that the hepatic activity of hENT1 and hCNT1/2 transporters will determine the in vivo hepatic distribution and therefore the efficacy and/or toxicity of nucleoside drugs used to treat hepatic diseases.",
keywords = "Biliary efflux, Biliary excretion, Hepatic diseases, Human concentrative nucleoside transporters, Human equilibrative nucleoside transporters, Localization, mRNA, Nucleoside drugs, Phosphorylation, Protein expression",
author = "Rajgopal Govindarajan and Endres, {Christopher J.} and Dale Whittington and Edward LeCluyse and Mar{\cc}al Pastor-Anglada and Tse, {Chung Ming} and Unadkat, {Jashvant D.}",
year = "2008",
month = "9",
doi = "10.1152/ajpgi.00542.2007",
language = "English (US)",
volume = "295",
journal = "American Journal of Physiology",
issn = "0363-6135",
publisher = "American Physiological Society",
number = "3",

}

TY - JOUR

T1 - Expression and hepatobiliary transport characteristics of the concentrative and equilibrative nucleoside transporters in sandwich-cultured human hepatocytes

AU - Govindarajan, Rajgopal

AU - Endres, Christopher J.

AU - Whittington, Dale

AU - LeCluyse, Edward

AU - Pastor-Anglada, Marçal

AU - Tse, Chung Ming

AU - Unadkat, Jashvant D.

PY - 2008/9

Y1 - 2008/9

N2 - We previously reported that both the concentrative (hCNT) and equilibrative (hENT) nucleoside transporters are expressed in the human liver (21). Here we report a study that investigated the expression of these transporters (transcripts and proteins) and their role in the hepatobiliary transport of nucleosides/nucleoside drugs using sandwich-cultured human hepatocytes. In the hepatic tissue, the rank order of the mRNA expression of the transporters was hCNT1 ≈ hENT1 > hENT2 ≈ hCNT2 > hCNT3. In sandwich-cultured hepatocytes, the mRNA expression of hCNT2 and hENT2 was comparable to that in hepatic tissue, whereas the expression of corresponding transporters in the two-dimensional hepatocyte cultures was lower. Colocalization studies demonstrated predominant localization of these transporters at the sinusoidal membrane and of hENT1, hCNT1, and hCNT2 at the canalicular membrane. In the sandwich-cultured hepatocytes, ENTs were the major contributors to the transport of thymidine (hENT1, 63%; hENT2, 23%) or guanosine (hENT1, 53%; hENT2, 24%) into the hepatocytes followed by hCNT1 (10%) for thymidine or hCNT2 (23%) for guanosine. Although ribavirin was predominately transported (89%) into the hepatocytes by hENT1, fialuridine (FIAU) was transported by both hENT1 (30%) and hCNTs (61%). The extensively metabolized natural nucleosides were not effluxed into the bile, whereas significant biliary-efflux was observed of FIAU (19%), ribavirin (30%), and formycin B (35%). We conclude that the hepatic activity of hENT1 and hCNT1/2 transporters will determine the in vivo hepatic distribution and therefore the efficacy and/or toxicity of nucleoside drugs used to treat hepatic diseases.

AB - We previously reported that both the concentrative (hCNT) and equilibrative (hENT) nucleoside transporters are expressed in the human liver (21). Here we report a study that investigated the expression of these transporters (transcripts and proteins) and their role in the hepatobiliary transport of nucleosides/nucleoside drugs using sandwich-cultured human hepatocytes. In the hepatic tissue, the rank order of the mRNA expression of the transporters was hCNT1 ≈ hENT1 > hENT2 ≈ hCNT2 > hCNT3. In sandwich-cultured hepatocytes, the mRNA expression of hCNT2 and hENT2 was comparable to that in hepatic tissue, whereas the expression of corresponding transporters in the two-dimensional hepatocyte cultures was lower. Colocalization studies demonstrated predominant localization of these transporters at the sinusoidal membrane and of hENT1, hCNT1, and hCNT2 at the canalicular membrane. In the sandwich-cultured hepatocytes, ENTs were the major contributors to the transport of thymidine (hENT1, 63%; hENT2, 23%) or guanosine (hENT1, 53%; hENT2, 24%) into the hepatocytes followed by hCNT1 (10%) for thymidine or hCNT2 (23%) for guanosine. Although ribavirin was predominately transported (89%) into the hepatocytes by hENT1, fialuridine (FIAU) was transported by both hENT1 (30%) and hCNTs (61%). The extensively metabolized natural nucleosides were not effluxed into the bile, whereas significant biliary-efflux was observed of FIAU (19%), ribavirin (30%), and formycin B (35%). We conclude that the hepatic activity of hENT1 and hCNT1/2 transporters will determine the in vivo hepatic distribution and therefore the efficacy and/or toxicity of nucleoside drugs used to treat hepatic diseases.

KW - Biliary efflux

KW - Biliary excretion

KW - Hepatic diseases

KW - Human concentrative nucleoside transporters

KW - Human equilibrative nucleoside transporters

KW - Localization

KW - mRNA

KW - Nucleoside drugs

KW - Phosphorylation

KW - Protein expression

UR - http://www.scopus.com/inward/record.url?scp=53449102537&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=53449102537&partnerID=8YFLogxK

U2 - 10.1152/ajpgi.00542.2007

DO - 10.1152/ajpgi.00542.2007

M3 - Article

C2 - 18635603

AN - SCOPUS:53449102537

VL - 295

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6135

IS - 3

ER -