title: Transport of the sulfated, amidated bile acid, sulfolithocholyltaurine, into rat hepatocytes is mediated by Oatp1 and Oatp2.
abstract: The uptake of the sulfated bile acid sulfolithocholyltaurine (SLCT) was investigated in isolated rat hepatocytes and in HeLa cells transfected with complementary DNAs (cDNAs) of organic anion transporting polypeptides (Oatps) 1 and 2 cloned from rat liver. In hepatocytes, transport of SLCT was greatly reduced by bromosulfophthalein (BSP), estrone sulfate, the precursor bile acids cholyltaurine and lithocholyltaurine, and 4,4'-diisothiocyanostilbene-2-2'-disulfonic acid (DIDS). However, SLCT transport was insensitive to 4-methylumbelliferyl sulfate, harmol sulfate, digoxin, fexofenadine, and lack of sodium ion. Because the estimation of kinetic constants was enhanced with use of inhibitors, BSP (1-50 micromol/L) was added to isolated rat hepatocytes to assess the various transport components for SLCT uptake. The resulting data showed a nonsaturable pathway and at least 2 pathways of different Michaelis-Menten constants (K(m)) (70 and 6 micromol/L) and similar maximum velocities (V(max)) (1.73 and 1.2 nmol/min/mg protein) and inhibition constants of 0.63 and 10.3 micromol/L for BSP. In expression systems, SLCT was taken up by Oatp1 and Oatp2 expressed in HeLa cells with similar K(m) values (12.6 +/- 6.2 and 14.6 +/- 1.9 micromol/L). These K(m) values were comparable to that observed for the high-affinity pathway in rat hepatocytes. In conclusion, the results suggest that transport of SLCT into rat liver is mediated in part by Oatp1 and Oatp2, high-affinity pathways, a lower-affinity pathway of unknown origin, and a nonsaturable pathway that is compatible with a transport system of high K(m) and/or passive diffusion.
authors: Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada.
authors: Ling-Jie
authors: LJ
authors: Meng
authors: Pijun
authors: P
authors: Wang
authors: Allan W
authors: AW
authors: Wolkoff
authors: Richard B
authors: RB
authors: Kim
authors: Rommel G
authors: RG
authors: Tirona
authors: Alan F
authors: AF
authors: Hofmann
authors: K Sandy
authors: KS
authors: Pang
mesh_terms: D000818:Animals; D000838:Anions / Q000494:pharmacology; D002756:Cholagogues and Choleretics / Q000493:pharmacokinetics*; D002794:Choline / Q000494:pharmacology; D015870:Gene Expression; D006367:HeLa Cells; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007202:Indicators and Reagents / Q000494:pharmacology; D027381:Liver-Specific Organic Anion Transporter 1 / Q000235:genetics / Q000378:metabolism; D008297:Male; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013431:Sulfates / Q000493:pharmacokinetics*; D013448:Sulfobromophthalein / Q000494:pharmacology; D013658:Taurolithocholic Acid / Q000493:pharmacokinetics*; D013696:Temperature
chemical_list: D000838:Anions; D002756:Cholagogues and Choleretics; D007202:Indicators and Reagents; D027381:Liver-Specific Organic Anion Transporter 1; D029362:Organic Anion Transporters, Sodium-Independent; C421102:Slco1a1 protein, rat; D013431:Sulfates; D013448:Sulfobromophthalein; D013658:Taurolithocholic Acid; D002794:Choline