Mediates the Na(+)-independent transport of organic anions such as steroid sulfate conjugates (dehydroepiandrosterone sulfate (DHEAS), 17-beta-glucuronosyl estradiol, estrone-3-sulfate), conjugated (taurocholate) and unconjugated (cholate) bile acids, prostaglandin E2 (PGE2) and L-thyroxine T4. Also capable of transporting sulfobromophthalein (BSP), ouabain and gadoxetate. Hydrogencarbonate/HCO3(-) acts as the probable counteranion that exchanges for organic anions. Shows a pH-sensitive substrate specificity which may be ascribed to the protonation state of the binding site and leads to a stimulation of substrate transport in an acidic microenvironment