Mediates the Na(+)-independent transport of organic anions such as taurocholate, the prostaglandins PGD2, PGE1, PGE2, leukotriene C4, thromboxane B2 and iloprost. Isoform 1 has it's highest expression in brain, it is the major form expressed in duodenum, kidney, placenta, and skeletal muscle. Isoform 3 predominates in liver. Functional transporter. Predominant isoform in liver, expression at promoter is regulated by HNF4alpha. Belongs to the organo anion transporter (TC 2.A.60) family. Extended N-terminus.