Nucleoside transport in human colonic epithelial cell lines: evidence for two Na+-independent transport systems in T84 and Caco-2 cells.
RT-PCR of RNA isolated from monolayers of the human colonic epithelial cell lines T84 and Caco-2 demonstrated the presence of mRNA for the two cloned Na+-independent equilibrative nucleoside transporters, ENT1 and ENT2, but not for the cloned Na+-dependent concentrative nucleoside transporters, CNT1 and CNT2. Uptake of [3H]uridine by cell monolayers in balanced Na+-containing and Na+-free media confirmed the presence of only Na+-independent nucleoside transport mechanisms. This uptake was decreased by 70-75% in the presence of 1 microM nitrobenzylthioinosine, a concentration that completely inhibits ENT1, and was completely blocked by the addition of 10 microM dipyridamole, a concentration that inhibits both ENT1 and ENT2. These findings indicate the presence in T84 and Caco-2 cells of two functional Na+-independent equilibrative nucleoside transporters, ENT1 and ENT2.
Ward
J L
JL
Department of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Ross 925, 720 Rutland Avenue, Baltimore, MD 21205, USA.
Tse
C M
CM
D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D033703:Nucleoside Transport Proteins; D013868:Thioinosine / Q000031:analogs & derivatives
D002352:Carrier Proteins; D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D008565:Membrane Proteins; D033703:Nucleoside Transport Proteins; C438654:SLC29A2 protein, human; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine