Contribution of organic anion transporters to the renal uptake of anionic compounds and nucleoside derivatives in rat

Our previous kinetic analyses have shown that rat organic anion transporter 1 (rOat1; Slc22a6) and rOat3 (Slc22a8) are responsible for the renal uptake of p-aminohippurate and pravastatin, respectively. In this study, their contribution to the renal uptake of organic anions and nucleoside derivatives was examined by investigating the uptake by rOat1- and rOat3-expressing cells and kidney slices. Transfection of rOat1 resulted in an increase of the uptake of temocaprilat (K-m = 0.56 muM), 2,4-dichlorophenoxyacetate (2,4-D; K-m = 10 muM), and 3'-azido-3'-deoxythymidine (AZT; K-m = 43 muM). rOat3-expressing cells showed significant uptake of temocaprilat (K-m = 1.4 muM), estrone sulfate (K-m = 5.3 muM), dehydroepiandrosterone sulfate (DHEAS; K-m = 12 muM), and benzylpenicillin (PCG; K-m = 85 muM). All the test compounds were accumulated in kidney slices in a carrier-mediated manner, although the saturable components of AZT and acyclovir were small. The K-m of 2,4-D uptake by kidney slices was comparable with that of rOat1, and the corresponding values of DHEAS and PCG were similar to those of rOat3. The uptake of estrone sulfate and temocapilat by kidney slices consisted of two saturable components, with the K-m values of their high-affinity components being similar to those for rOat3 ( estrone sulfate), and rOat1 and rOat3 ( temocaprilat), respectively. These results suggest that the renal uptake of 2,4-D is mainly accounted for by rOat1 and the uptake of PCG and DHEAS by rOat3, and rOat3 is partly involved in the renal uptake of temocaprilat and estrone sulfate.