Role of organic anion transporter 3 (Oat3) in the renal transport of glutathione (GSH)

GSH transport across the basolateral plasma membrane (BLM) into the renal proximal tubule occurs by both sodium‐coupled and sodium‐independent pathways and may be mediated by one or more of several carriers, including organic anion transporters 1 and 3 (Oat1 [Slc22a6] and Oat3 [Slc22a8]). Bacterially expressed and reconstituted rat Oat3 transported both GSH and p‐aminohippurate (PAH) in exchange for 2‐oxoglutarate (2‐OG) and 2‐OG and PAH in exchange for GSH, and PAH uptake was inhibited by both probenecid and furosemide, consistent with the function of Oat3. To investigate the function of Oat3 in GSH uptake in an intact cellular model, NRK‐52E cells was assessed. Analysis of mRNA expression by RT‐PCR of Oat3 and other potential carriers in homogenates of both rat kidney cortex and NRK‐52E cells revealed that whereas rat kidney cortex expressed all the potential GSH carriers (i.e., Oat1, Oat3, the sodium‐dicarboxylate carrier 2 [NaC2; Slc13a3], organic anion transporting polypeptide 1a1 [Oatp1a1; Slco1a1], and multidrug resistance proteins 2 and 5 [Mrp2/5; Abcc2/5]), NRK‐52E cells failed to show any expression. Little PAH‐ or 2‐OG‐stimulated GSH uptake was detected across the BLM of NRK‐52E cells. We conclude that Oat3 can function in GSH uptake and that NRK‐52E cells possess a low background rate of GSH uptake and can thus be a good model for overexpression of specific, putative GSH carriers.