Polyspecific substrate uptake by the hepatic organic anion transporter Oatp1 in stably transfected CHO cells.
The rat liver organic anion transporting polypeptide (Oatp1) has been extensively characterized mainly in the Xenopus laevis expression system as a polyspecific carrier transporting organic anions (bile salts), neutral compounds, and even organic cations. In this study, we extended this characterization using a mammalian expression system and confirm the basolateral hepatic expression of Oatp1 with a new antibody. Besides sulfobromophthalein [Michaelis-Menten constant (Km) of approximately 3 microM], taurocholate (Km of approximately 32 microM), and estradiol- 17beta-glucuronide (Km of approximately 4 microM), substrates previously shown to be transported by Oatp1 in transfected HeLa cells, we determined the kinetic parameters for cholate (Km of approximately 54 microM), glycocholate (Km of approximately 54 microM), estrone-3-sulfate (Km of approximately 11 microM), CRC-220 (Km of approximately 57 microM), ouabain (Km of approximately 3,000 microM), and ochratoxin A (Km of approximately 29 microM) in stably transfected Chinese hamster ovary (CHO) cells. In addition, three new substrates, taurochenodeoxycholate (Km of approximately 7 microM), tauroursodeoxycholate (Km of approximately 13 microM), and dehydroepiandrosterone sulfate (Km of approximately 5 microM), were also investigated. The results establish the polyspecific nature of Oatp1 in a mammalian expression system and definitely identify conjugated dihydroxy bile salts and steroid conjugates as high-affinity endogenous substrates of Oatp1.
Eckhardt
U
U
Division of Clinical Pharmacology and Toxicology, Department of Medicine, University Hospital, CH-8091 Zurich, Switzerland.
Schroeder
A
A
Stieger
B
B
Höchli
M
M
Landmann
L
L
Tynes
R
R
Meier
P J
PJ
Hagenbuch
B
B
D000818:Animals; D027321:Anion Transport Proteins; D016466:CHO Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D019826:Cholic Acid / Q000493:pharmacokinetics; D006224:Cricetinae; D019314:Dehydroepiandrosterone Sulfate / Q000493:pharmacokinetics; D004151:Dipeptides / Q000493:pharmacokinetics; D004958:Estradiol / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D004970:Estrone / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D006000:Glycocholic Acid / Q000493:pharmacokinetics; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009793:Ochratoxins / Q000493:pharmacokinetics; D010042:Ouabain / Q000493:pharmacokinetics; D010880:Piperidines / Q000493:pharmacokinetics; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013448:Sulfobromophthalein / Q000493:pharmacokinetics; D013655:Taurochenodeoxycholic Acid / Q000493:pharmacokinetics; D013656:Taurocholic Acid / Q000493:pharmacokinetics; D014162:Transfection; D014982:Xenopus laevis
D027321:Anion Transport Proteins; C093375:CRC 220; D002352:Carrier Proteins; D004151:Dipeptides; D009793:Ochratoxins; D010880:Piperidines; D011994:Recombinant Proteins; D013448:Sulfobromophthalein; C025589:ochratoxin A; C025483:estradiol-17 beta-glucuronide; D004970:Estrone; D004958:Estradiol; D013655:Taurochenodeoxycholic Acid; D019314:Dehydroepiandrosterone Sulfate; D010042:Ouabain; D013656:Taurocholic Acid; C031655:ursodoxicoltaurine; D019826:Cholic Acid; D006000:Glycocholic Acid; C017296:estrone sulfate