TY - JOUR T1 - Carrier-Mediated Active Transport of a Novel Thromboxane A<sub>2</sub> Receptor Antagonist [2-(4-Chlorophenylsulfonylaminomethyl)indan-5-yl]acetate (Z-335) into Rat Liver JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 498 LP - 504 DO - 10.1124/dmd.30.5.498 VL - 30 IS - 5 AU - Yoshihiro Kawabata AU - Shigeru Furuta AU - Yutaka Shinozaki AU - Tadashi Kurimoto AU - Ryuichiro Nishigaki Y1 - 2002/05/01 UR - http://dmd.aspetjournals.org/content/30/5/498.abstract N2 - To elucidate the transport system by which [2-(4-chlorophenylsulfonylaminomethyl)indan-5-yl]acetate (Z-335) is taken up into the liver, we investigated the uptake characteristics of Z-335 in isolated rat hepatocytes. In addition, we estimated the hepatic uptake of Z-335 in intact rats under steady-state conditions and compared it with the in vitro uptake clearance. Uptake of Z-335 is highly concentrative (cell-to-medium concentration ratios were 21.2 at 0.5 min and 71.7 at 5 min), temperature-dependent, and sensitive to metabolic inhibitors, indicating that uptake is mediated by energy-dependent uphill transport. In the presence of metabolic inhibitors [carbonyl cyanidep-trifluoromethoxyphenylhydrazone and rotenone], uptake remained at 37 and 49% of the control value, respectively, suggesting that ATP-independent uptake contributes to the total uptake of Z-335. The concentration dependence of the initial uptake velocity indicated a two-component process, one saturable component, with aKm value of 45.6 μM and aVmax value of 4.1 nmol/min/mg of protein, and a nonspecific diffusion clearance, with aPdif value of 8.3 μl/min/mg of protein. The contribution of the carrier-mediated uptake to the total uptake in a linear range was estimated as 91%. The in vivo hepatic intrinsic clearance (CLint, app) was comparable with that in vitro uptake clearance (PSinflux) and indicated that the CLint, app of Z-335 at steady state is rate-limited by the uptake process. In conclusion, hepatic intrinsic clearance of Z-335 at steady state is rate-limited by the uptake process since Z-335 is efficiently taken up by an active transport mechanism, followed by metabolism or biliary excretion. The American Society for Pharmacology and Experimental Therapeutics ER -