Functional and immunochemical characterization of a novel organic anion transporter Oat8 (Slc22a9) in rat renal collecting duct.

In this study, we demonstrate that a putative membrane unknown solute transporter 1 of the rat kidney (UST1r; Slc22a9) is a multispecific transporter of organic anions (OAs). When expressed in Xenopus oocytes, UST1r mediated uptake of ochratoxin A (OTA; K(m) = 1.0 microM) and sulfate conjugates of steroids, such as estrone-3-sulfate (ES; K(m) = 3.