title: Saturable Hepatic Extraction of Gemcitabine Involves Biphasic Uptake Mediated by Nucleoside Transporters Equilibrative Nucleoside Transporter 1 and 2.
abstract: Hepatic arterial infusion (HAI) chemotherapy with gemcitabine (GEM) is expected to be more effective and safer method to treat hepatic metastasis of pancreatic cancer compared with intravenous administration, because it affords higher tumor exposure with lower systemic exposure. Thus, a key issue for dose selection is the saturability of hepatic uptake of GEM. Therefore, we investigated GEM uptake in rat and human isolated hepatocytes. Hepatic GEM uptake involved high- and low-affinity saturable components with Km values of micromolar and millimolar order, respectively. The uptake was inhibited concentration dependently by S-(4-nitrobenzyl)-6-thioinosine (NBMPR) and was sodium-ion-independent, suggesting a contribution of equilibrative nucleoside transporters (ENTs). The concentration dependence of uptake in the presence of 0.1 μM NBMPR showed a single low-affinity binding site. Therefore, the high- and low-affinity sites correspond to ENT1 and ENT2, respectively. Our results indicate hepatic extraction of GEM is predominantly mediated by the low-affinity site (hENT2), and at clinically relevant hepatic concentrations of GEM, hENT2-mediated uptake would not be completely saturated. This is critical for HAI, because saturation of hepatic uptake would result in a marked increase of GEM concentration in the peripheral circulation, abrogating the advantage of HAI over intravenous administration in terms of severe adverse events.
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.|Department of Membrane Transport and Biopharmaceutics, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Department of Membrane Transport and Biopharmaceutics, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Department of Gastroenterologic Surgery, Division of Cancer Medicine, Graduate School of Medical Sciences, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Tajima
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Yamazaki
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Rina
authors.initials: R
authors.lastname: Yokono
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Takabayashi
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Sawamoto
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Department of Gastroenterologic Surgery, Division of Cancer Medicine, Graduate School of Medical Sciences, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Kitagawa
authors.affiliation: Department of Gastroenterologic Surgery, Division of Cancer Medicine, Graduate School of Medical Sciences, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ohta
authors.affiliation: Department of Membrane Transport and Biopharmaceutics, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Ikumi
authors.initials: I
authors.lastname: Tamai
authors.affiliation: Department of Hospital Pharmacy, University Hospital, Kanazawa University, Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Sai
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism; D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2 / Q000378:metabolism; D005260:Female; D006499:Hepatic Artery / Q000187:drug effects / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007260:Infusion Pumps; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008875:Middle Aged; D051381:Rats; D017208:Rats, Wistar; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000093542:Gemcitabine
chemical_list: D002352:Carrier Proteins; D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D008565:Membrane Proteins; C438652:Slc29a1 protein, rat; D003841:Deoxycytidine; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine; D000093542:Gemcitabine
keywords: cancer; equilibrative nucleoside transporter; hepatic transport; hepatocytes; kinetics ; transporters