title: Involvement of concentrative nucleoside transporter 1 in intestinal absorption of trifluorothymidine, a novel antitumor nucleoside, in rats.
abstract: ααα-Trifluorothymidine (TFT), an anticancer nucleoside analog, is a potent thymidylate synthase inhibitor. TFT exerts its antitumor activity primarily by inducing DNA fragmentation after incorporation of the triphosphate form of TFT into the DNA. Although an oral combination of TFT and a thymidine phosphorylase inhibitor has been clinically developed, there is little information regarding TFT absorption. Therefore, we investigated TFT absorption in the rat small intestine. After oral administration of TFT in rats, more than 75% of the TFT was absorbed. To identify the uptake transport system, uptake studies were conducted by using everted sacs prepared from rat small intestines. TFT uptake was saturable, significantly reduced under Na(+)-free conditions, and strongly inhibited by the addition of an endogenous pyrimidine nucleoside. From these results, we suggested the involvement of concentrative nucleoside transporters (CNTs) in TFT absorption into rat small intestine. In rat small intestines, the mRNAs coding for rat CNT1 (rCNT1) and rCNT2, but not for rCNT3, were predominantly expressed. To investigate the roles of rCNT1 and rCNT2 in TFT uptake, we conducted uptake assays by using Xenopus laevis oocytes injected with rCNT1 complementary RNA (cRNA) and rCNT2 cRNA. TFT uptake by X. laevis oocytes injected with rCNT1 cRNA, and not rCNT2 cRNA, was significantly greater than that by water-injected oocytes. In addition, in situ single-pass perfusion experiments performed using rat jejunum regions showed that thymidine, a substrate for CNT1, strongly inhibited TFT uptake. In conclusion, TFT is absorbed via rCNT1 in the intestinal lumen in rats.
authors.affiliation: Tokushima Research Center, Taiho Pharmaceutical Co., Ltd, 224-2 Ebisuno, Hiraishi, Kawauchi-cho, Tokushima 771-0194, Japan. t-okayama@taiho.co.jp
authors.forename: Takashige
authors.initials: T
authors.lastname: Okayama
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Yoshisue
authors.forename: Keizo
authors.initials: K
authors.lastname: Kuwata
authors.forename: Masahito
authors.initials: M
authors.lastname: Komuro
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ohta
authors.forename: Sekio
authors.initials: S
authors.lastname: Nagayama
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D001667:Binding, Competitive / Q000502:physiology; D004347:Drug Interactions / Q000502:physiology; D005260:Female; D007288:Inosine / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D007413:Intestinal Mucosa / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010477:Perfusion / Q000379:methods; D012313:RNA / Q000008:administration & dosage / Q000235:genetics / Q000302:isolation & purification; D018075:RNA, Complementary / Q000008:administration & dosage / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D019810:Sodium Azide / Q000494:pharmacology; D013936:Thymidine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D013939:Thymidine Phosphorylase / Q000037:antagonists & inhibitors; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors; D014271:Trifluridine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D014529:Uridine / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: C506441:5-chloro-6-(2-imino-propyrrolidin-1-yl) methyl-2,4 (1H, 3H)-pyrimidinedione hydrochloride; D000970:Antineoplastic Agents; D026901:Membrane Transport Proteins; D018075:RNA, Complementary; C065171:cif nucleoside transporter; D007288:Inosine; D012313:RNA; D019810:Sodium Azide; D013940:Thymidylate Synthase; D013939:Thymidine Phosphorylase; D019297:2,4-Dinitrophenol; D014271:Trifluridine; D013936:Thymidine; D014529:Uridine