title: Inhibition of carrier-mediated uptake of epirubicin reduces cytotoxicity in primary culture of rat hepatocytes.
abstract: Epirubicin, an antineoplastic drug, is considered to be taken up by tumor cells via a common carrier by facilitated diffusion and is then pumped out in an energy-dependent manner because epirubicin is a substrate for P-glycoprotein (P-gp). However, this study investigated the details of the influx mechanism of epirubicin and demonstrated that epirubicin uptake was mediated by active carrier systems in addition to facilitated diffusion in the primary culture of rat hepatocytes. The uptake of epirubicin gradually increased in a saturated manner when the concentrations were between 1 x 10(-7) M and 1 x 10(-6) M. In contrast, the uptake increased progressively in a linear manner when the concentration was high (greater than 1 x 10(-6) M). The uptake of epirubicin at a clinical concentration (7.5 x 10(-7) M) was significantly reduced at 4 degrees C and significantly inhibited when pretreated with metabolic inhibitors (carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), rotenone and sodium azide) by nearly 25%. Furthermore, an organic anion transporter inhibitor, namely, 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS); organic anion transport substrates, namely, para-aminohippurate (PAH), taurocholic acid and estradiol 17-beta-D-glucuronide; and organic cation transporter inhibitors, namely, verapamil and tetraethylammonium significantly reduced the uptake of epirubicin. Furthermore, pretreatment with verapamil and PAH significantly prevented epirubicin-induced reduction of proliferative activity in rat hepatocytes. These results indicated that the uptake of epirubicin was induced, at least in part, by the active transport protein in rat hepatocytes; the inhibition of the probable transport protein protected the intact normal cells from the injury induced by the cytotoxicity of epirubicin.
authors.affiliation: Department of Pharmacy, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake-cho, Miyazaki 889-1692, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Iwakiri
authors.forename: Manabu
authors.initials: M
authors.lastname: Okumura
authors.forename: Muneaki
authors.initials: M
authors.lastname: Hidaka
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kumagai
authors.forename: Emi
authors.initials: E
authors.lastname: Ichihara
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawano
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Arimori
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism* / Q000633:toxicity; D001693:Biological Transport, Active / Q000187:drug effects / Q000235:genetics; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D015251:Epirubicin / Q000378:metabolism* / Q000633:toxicity; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009570:Nitriles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012402:Rotenone / Q000494:pharmacology; D019810:Sodium Azide / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D010130:p-Aminohippuric Acid / Q000494:pharmacology
chemical_list: D000903:Antibiotics, Antineoplastic; D002352:Carrier Proteins; D009570:Nitriles; D014475:Uncoupling Agents; D012402:Rotenone; C100076:mesoxalonitrile; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D015251:Epirubicin; D019810:Sodium Azide; D014700:Verapamil; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D010130:p-Aminohippuric Acid