TY - JOUR T1 - Transporter Studies with the 3-<em>O</em>-Sulfate Conjugate of 17α-Ethinylestradiol: Assessment of Human Liver Drug Transporters JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1072 LP - 1082 DO - 10.1124/dmd.109.031518 VL - 38 IS - 7 AU - Yong-Hae Han AU - Dennis Busler AU - Yang Hong AU - Yuan Tian AU - Cliff Chen AU - A. David Rodrigues Y1 - 2010/07/01 UR - http://dmd.aspetjournals.org/content/38/7/1072.abstract N2 - 17α-Ethinylestradiol (EE2), a component of oral contraceptives, is known to undergo considerable first-pass 3-O-sulfation in the intestine and liver. Once formed, the 3-O-sulfate conjugate (EE2-Sul) is detected in circulation at appreciable levels (versus parent EE2) and is present in bile. Therefore, hepatic uptake of EE2-Sul was assessed with suspensions of cryopreserved human primary hepatocytes. In this instance, there was evidence for active (temperature-dependent) uptake, which was described by a two-Km (Michaelis constant) model (Km1 = 220 nM; Km2 = 15.5 μM). Uptake was inhibited (∼90%) by bromosulfophthalein but not by tetraethylammonium or p-aminohippurate. In agreement, EE2-Sul was shown to be a substrate of recombinant organic anion transporter peptides (OATP1B1 and OATP2B1), and Na+/taurocholate-cotransporting polypeptide (NTCP), expressed individually in human embryonic kidney (HEK) 293 cells. Transport by OATP1B1 was described by two Km values (87 nM and 141 μM), whereas OATP2B1- and NTCP-mediated uptake into HEK-293 cells conformed to single Km kinetics (10.7 and 2.6 μM, respectively). EE2-Sul was also assessed as an efflux transporter substrate using membrane vesicles expressing bile salt export pump, breast cancer resistance protein (BCRP), and individual forms of multidrug resistance-associated protein (MRP1, MRP2, and MRP3). Transport studies were also conducted with a cell line expression P-glycoprotein. Only vesicles that contained BCRP exhibited ATP-dependent uptake of EE2-Sul (Km1 = 2.9 and Km2 = 307 μM). Collectively, the data show that hepatic uptake of EE2-Sul can be mediated by three transporters (OATP1B1, OATP2B1, and NTCP), whereas biliary excretion of EE2-Sul into bile likely involves BCRP. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics ER -