TY - JOUR T1 - Organic Anion Transporter 3 (Oat3/<em>Slc22a8</em>) Interacts with Carboxyfluoroquinolones, and Deletion Increases Systemic Exposure to Ciprofloxacin JF - Molecular Pharmacology JO - Mol Pharmacol SP - 122 LP - 131 DO - 10.1124/mol.107.042853 VL - 74 IS - 1 AU - Adam L. VanWert AU - Chutima Srimaroeng AU - Douglas H. Sweet Y1 - 2008/07/01 UR - http://molpharm.aspetjournals.org/content/74/1/122.abstract N2 - Carboxyfluoroquinolones, such as ciprofloxacin, are used for the treatment of numerous infectious diseases. Renal secretion is a major determinant of their systemic and urinary concentration, but the specific transporters involved are virtually unknown. In vivo studies implicate the organic anion transporter (OAT) family as a pivotal component of carboxyfluoroquinolone renal secretion. Therefore, this study identified the specific renal basolateral OAT(s) involved, thereby highlighting potential sources of carboxyfluoroquinolone-drug interactions and variable efficacy. Two heterologous expression systems, Xenopus laevis oocytes and cell monolayers, were used to determine the roles of murine and human renal basolateral mOat1/hOAT1 and mOat3/hOAT3. Ciprofloxacin was transported by mOat3 in both systems (Km value, 70 ± 6 μM) and demonstrated no interaction with mOat1 or hOAT1. Furthermore, ciprofloxacin, norfloxacin, ofloxacin, and gatifloxacin exhibited concentration-dependent inhibition of transport on mOat3 in cells with inhibition constants of 198 ± 39, 558 ± 75, 745 ± 165, and 941 ± 232 μM, respectively. Ciprofloxacin and gatifloxacin also inhibited hOAT3. Thereafter, in vivo elimination of ciprofloxacin was assessed in wild-type and Oat3 null mice [Oat3(-/-)]. Oat3(-/-) mice exhibited significantly elevated plasma levels of ciprofloxacin at clinically relevant concentrations (P &lt; 0.05, male mice; P &lt; 0.01, female mice). Oat3(-/-) mice also demonstrated a reduced volume of distribution (27%, P &lt; 0.01, male mice; 14%, P &lt; 0.01, female mice) and increased area under the concentration-time curve (25%, P &lt; 0.05, male mice; 33%, P &lt; 0.01, female mice). Female Oat3(-/-) mice had a 35% (P &lt; 0.01) reduction in total clearance of ciprofloxacin relative to wild type. In addition, putative ciprofloxacin metabolites were significantly elevated in Oat3(-/-) mice. The present findings indicate that polymorphisms of and drug interactions on hOAT3 may influence carboxyfluoroquinolone efficacy, especially in urinary tract infections. The American Society for Pharmacology and Experimental Therapeutics ER -