Characterization of bile acid transport mediated by multidrug resistance associated protein 2 and bile salt export pump.
Biliary excretion of certain bile acids is mediated by multidrug resistance associated protein 2 (Mrp2) and the bile salt export pump (Bsep). In the present study, the transport properties of several bile acids were characterized in canalicular membrane vesicles (CMVs) isolated from Sprague--Dawley (SD) rats and Eisai hyperbilirubinemic rats (EHBR) whose Mrp2 function is hereditarily defective and in membrane vesicles isolated from Sf9 cells infected with recombinant baculovirus containing cDNAs encoding Mrp2 and Bsep. ATP-dependent uptake of [(3)H]taurochenodeoxycholate sulfate (TCDC-S) (K(m)=8.8 microM) and [(3)H]taurolithocholate sulfate (TLC-S) (K(m)=1.5 microM) was observed in CMVs from SD rats, but not from EHBR. In addition, ATP-dependent uptake of [(3)H]TLC-S (K(m)=3.9 microM) and [(3)H]taurocholate (TC) (K(m)=7.5 microM) was also observed in Mrp2- and Bsep-expressing Sf9 membrane vesicles, respectively. TCDC-S and TLC-S inhibited the ATP-dependent TC uptake into CMVs from SD rats with IC(50) values of 4.6 microM and 1.2 microM, respectively. In contrast, the corresponding values for Sf9 cells expressing Bsep were 59 and 62 microM, respectively, which were similar to those determined in CMVs from EHBR (68 and 33 microM, respectively). By co-expressing Mrp2 with Bsep in Sf9 cells, IC(50) values for membrane vesicles from these cells shifted to values comparable with those in CMVs from SD rats (4.6 and 1.2 microM). Moreover, in membrane vesicles where both Mrp2 and Bsep are co-expressed, preincubation with the sulfated bile acids potentiated their inhibitory effect on Bsep-mediated TC transport. These results can be accounted for by assuming that the sulfated bile acids trans-inhibit the Bsep-mediated transport of TC.
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan.
H
H
Akita
H
H
Suzuki
K
K
Ito
S
S
Kinoshita
N
N
Sato
H
H
Takikawa
Y
Y
Sugiyama
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001647:Bile Acids and Salts / Q000378:metabolism*; D001648:Bile Canaliculi / Q000378:metabolism; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013655:Taurochenodeoxycholic Acid / Q000378:metabolism; D013656:Taurocholic Acid / Q000378:metabolism; D013658:Taurolithocholic Acid / Q000378:metabolism; D014316:Tritium
D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; C490548:Abcb11 protein, rat; C423013:Abcc2 protein, rat; D001647:Bile Acids and Salts; D002352:Carrier Proteins; D014316:Tritium; D013655:Taurochenodeoxycholic Acid; D013658:Taurolithocholic Acid; D013656:Taurocholic Acid