Pharmacological analysis and molecular cloning of the canine equilibrative nucleoside transporter 1

Eur J Pharmacol. 2004 Apr 26;491(1):9-19. doi: 10.1016/j.ejphar.2004.03.026.


We studied the binding of [3H]nitrobenzylthioinosine (NBMPR) and the uptake of [3H]formycin B by the es (equilibrative inhibitor-sensitive) nucleoside transporter of Madin Darby Canine Kidney (MDCK) cells. NBMPR inhibited [3H]formycin B uptake with a Ki of 2.7+/-0.6 nM, and [3H]NBMPR had a KD of 1.3+/-0.3 nM for binding to these cells; these values are significantly higher than those obtained in human and mouse cell models. In contrast, other recognized es inhibitors, such as dipyridamole, were significantly more effective as inhibitors of [3H]NBMPR binding and [3H]formycin B uptake by MDCK cells relative to that seen for human cells. We isolated a cDNA encoding the canine es nucleoside transporter (designated cENT1), and assessed its function by stable expression in nucleoside transport deficient PK15NTD cells. The PK15-cENT1 cells displayed inhibitor sensitivities that were comparable to those obtained for the endogenous es nucleoside transporter in MDCK cells. These data indicate that the dog es/ENT1 transporter has distinctive inhibitor binding characteristics, and that these characteristics are a function of the protein structure as opposed to the environment in which it is expressed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding, Competitive / drug effects
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cell Line
  • Cloning, Molecular
  • DNA, Complementary / chemistry
  • DNA, Complementary / genetics
  • Dilazep / pharmacology
  • Dipyridamole / pharmacology
  • Dogs
  • Dose-Response Relationship, Drug
  • Equilibrative Nucleoside Transporter 1 / chemistry
  • Equilibrative Nucleoside Transporter 1 / genetics*
  • Equilibrative Nucleoside Transporter 1 / metabolism
  • Formycins / metabolism
  • Kinetics
  • Molecular Sequence Data
  • Piperazines / pharmacology
  • Protein Binding / drug effects
  • Protein Conformation
  • Radioligand Assay
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Thioinosine / analogs & derivatives*
  • Thioinosine / metabolism
  • Tritium


  • Carrier Proteins
  • DNA, Complementary
  • Equilibrative Nucleoside Transporter 1
  • Formycins
  • Piperazines
  • draflazine
  • Tritium
  • formycin B
  • Thioinosine
  • Dipyridamole
  • Dilazep
  • 4-nitrobenzylthioinosine

Associated data

  • GENBANK/AY587107
  • GENBANK/AY587108