Table 1

Inhibition of uridine uptake in ARAC/D2 cells by ribonucleosides, arabinonucleosides, and nucleobases: identification of candidate permeants and inhibitors of hCNT2

Additive (Test Compound)Net [3H]Uridine Transport
% control
Pyrimidine nucleosides, nucleobases, ribose and dilazep
 None100
 Uridine2  ± 0.8
 5-Fluorouridine1  ± 0.6
 5-Bromouridine7  ± 5
 5-Iodouridine9  ± 7
 5-Methyluridine38  ± 3
 2′-Deoxyuridine3  ± 1.4
 3′-Deoxyuridine99  ± 7
 2′,3′-Dideoxyuridine101  ± 5
 5-Fluoro-2′-deoxyuridine18  ± 2
 5-Bromo-2′-deoxyuridine56  ± 3
 5-Iodo-2′-deoxyuridine69  ± 5
 5-Fluoro-5′-deoxyuridine80  ± 5
 Thymidine74  ± 3
 Cytidine94  ± 7
 2′-Deoxycytidine96  ± 6
 Uracil68  ± 3
 5-Fluorouracil82  ± 3
 Thymine85  ± 2
 Cytosine99  ± 5
 Ribose97  ± 4
 Dilazep88  ± 3
Purine nucleosides and nucleobases
 Inosine4  ± 2.8
 2′-Deoxyinosine5  ± 4
 Guanosine1  ± 0.8
 2′-Deoxyguanosine3  ± 2
 Adenosine2  ± 1.7
 2′-Deoxyadenosine2  ± 1.3
 2′,3′-Dideoxyadenosine96  ± 3
 2-Chloroadenosine15  ± 3
 2-Chloro-2′-deoxyadenosine72  ± 4
 7-Deazaadenosine100  ± 2
 Adenine98  ± 3
 Hypoxanthine96  ± 5
 Guanine101  ± 2
Arabinonucleosides and arabinose
 1-β-d-Arabinofuranosyluracil70  ± 4
 1-β-d-Arabinofuranosylcytosine102  ± 6
 9-β-d-Arabinofuranosyladenine31  ± 2
 2-Fluoro-9-β-d-arabinofuranosyladenine84  ± 3
 9-β-d-Arabinofuranosylhypoxanthine20  ± 2
 Arabinose99  ± 3

Rates of transport of 10 μM [3H]uridine obtained from 3 to 4-min time courses similar to those shown in Fig. 3 were conducted in Na+-containing and Na+-free transport buffer in the absence and presence of 1 mM test compounds listed. Uridine transport values in the absence of additives (controls) ranged from 0.1 ± 0.005 pmol/μl cell water/s to 0.12 ± 0.013 pmol/μl cell water/s. Net transport rates are the Na+-dependent component expressed as percentage of control values and are means ± S.D. of triplicate determinations.