NPT1, also called sodium-dependent phosphate transport protein, belongs to the organic anion transporter family, SLC17A. It is mainly expressed in the kidney transporting small organic anions such as PAH (para-aminohippurate), but it is also found in the liver and brain. NTP1 localizes to the apical membrane of renal proximal tubular cells and functions as a voltage driven organic anion/Cl-exchanger. It also plays a role in maintaining phosphate homeostasis. The expression of NPT1 is transcriptionally regulated by HNF-1å and HNF-3∫. Indomethacin and salicylate inhibit NPT1-mediated PAH transport.