this invention is concerned with human organic anion transporter . isolated nucleic acid encoding hoat is provided , along with ioslated hoat polypeptide . hoat nucleic acid and / or hoat polypeptide are employed in transgenic animals , recombinant cells , replicable vectors and analytical procedures for identifying hoat agonists or antagonists , assays for identifying hoat alleles and / or isotypes , screening tests for nephrotoxic or neurologically active compounds , and determination of drug - drug interactions within the kidney or brain .