title: Ethacrynic-acid-induced glutathione depletion and oxidative stress in normal and Mrp2-deficient rat liver.
abstract: Oxidative stress in the liver is sometimes accompanied by cholestasis. We investigated the localization and role of multidrug-resistance-associated protein (Mrp) 2, a biliary transporter involved in bile-salt-independent bile flow, under ethacrynic acid (EA)-induced acute oxidative stress. Normal Sprague-Dawley rat (SDR) and Mrp2-deficient Eisai hyperbilirubinemic rat (EHBR) livers were perfused with 500 microM EA. The release of glutamic pyruvic transaminase (GPT) and thiobarbituric-acid-reactive substances (TBARS) from EHBR liver was markedly delayed compared with that from SDR liver. This is mainly due to the higher basal level of glutathione (GSH) in EHBR liver (59.1 +/- 0.3 nmol/mg protein) compared with SDR liver (39.7 +/- 1.5 nmol/mg protein). EA similarly induced a rapid reduction in GSH followed by mitochondrial permeability transition in the isolated mitochondria from both SDR and EHBR. Internalization of Mrp2 was detected before nonspecific disruption of the canalicular membrane and GPT release in SDR liver perfused with 100 microM EA. SDR liver preperfused with hyperosmolar buffer (405 mosmol/L) for 30 min induced internalization of Mrp2 without changing the basal GSH level, while elimination of hepatic GSH by 300 microM EA perfusion was significantly delayed thereafter. Concomitantly, hepatotoxicity assessed by the release of GPT and TBARS was also significantly attenuated under hyperosmolar conditions. In conclusion, preserved cytosolic and intramitochondrial GSH is the key factor involved in the acute hepatotoxicity induced by EA and its susceptibility could be altered by the presence of Mrp2.
authors.affiliation: Laboratory of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675, Japan.
authors.forename: Bin
authors.initials: B
authors.lastname: Ji
authors.forename: Kousei
authors.initials: K
authors.lastname: Ito
authors.forename: Shuichi
authors.initials: S
authors.lastname: Sekine
authors.forename: Ai
authors.initials: A
authors.lastname: Tajima
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Horie
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D000410:Alanine Transaminase / Q000032:analysis / Q000378:metabolism; D000818:Animals; D001648:Bile Canaliculi / Q000737:chemistry / Q000166:cytology; D004976:Ethacrynic Acid / Q000633:toxicity; D005978:Glutathione / Q000172:deficiency* / Q000378:metabolism; D006932:Hyperbilirubinemia / Q000378:metabolism*; D066298:In Vitro Techniques; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology; D008099:Liver / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; C423013:Abcc2 protein, rat; D017392:Thiobarbituric Acid Reactive Substances; D000410:Alanine Transaminase; D005978:Glutathione; D004976:Ethacrynic Acid