title: Pirarubicin is taken up by a uridine-transportable sodium-dependent concentrative nucleoside transporter in Ehrlich ascites carcinoma cells.
abstract: OBJECTIVE
  We evaluated the contribution of a nucleoside transporter (NT) consisting of an equilibrative NT (ENT) and a concentrative Na(+)/nucleoside cotransporter (CNT) to the uptake of THP and DOX by mouse Ehrlich ascites carcinoma cells. METHODS. Transport experiments were performed using a silicone layer method. The expression of CNT isoforms was confirmed by RT-PCR analysis.
  
  
  RESULTS
  The effects of inhibition of the ENT inhibitors, nitrobenzylthioinosine (NBMPR) and nitrobenzylthioguanosine, on THP and DOX uptake by Ehrlich cells was negligible. THP uptake, but not DOX uptake, partially depended on an inwardly directed Na(+) gradient, and the uptake was inhibited by all the inhibitors of CNT examined. Furthermore, efflux of [(3)H]uridine from Ehrlich cells was stimulated by the addition of THP to the extracellular compartment, which was definitive evidence of CNT-mediated uptake of THP. The mRNA for CNT2, but not that for CNT3, was detected in Ehrlich cells, which is consistent with the characteristics of [(3)H]uridine uptake. In the cells, formycin B, a representative CNT2 ligand, had cis-inhibitory and trans-stimulatory effects on THP uptake.
  
  
  CONCLUSIONS
  These results demonstrate that THP, but not DOX, is taken up into Ehrlich cells partially via a uridine-transportable CNT.
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, 607-8414, Kyoto, Japan.
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Nagai
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nagasawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ishimoto
authors.forename: Sadaki
authors.initials: S
authors.lastname: Fujimoto
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000378:metabolism*; D005573:Formycins / Q000494:pharmacology; D051379:Mice; D033703:Nucleoside Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000502:physiology*; D014407:Tumor Cells, Cultured; D014529:Uridine / Q000378:metabolism*
chemical_list: D000903:Antibiotics, Antineoplastic; D005573:Formycins; D033703:Nucleoside Transport Proteins; D012333:RNA, Messenger; C034561:formycin B; D004317:Doxorubicin; D012964:Sodium; C027260:pirarubicin; D014529:Uridine