Inorganic sulfate is an essential cofactor for sulfation in liver and kidney cells. In hepatocytes, the entry of innorganic sulfate via the sinusoidal membrane of rat hepatocytes is mediated by sat-1 (Slc26a1), whereas in kidneys sulfate can be taken up across the luminal membrane by NaS1 (Slc13a1) or across the basolateral membrane by sat-1. To test transport mode and substrate specificity, we expressed rat sat-1 in Xenopus laevis oocytes. [35S]sulfate uptake was inhibited, and [35S]sulfate efflux from preinjected oocytes was trans-stimulated, by bicarbonate and oxalate, indicating that sat-1 mediated sulfate-bicarbonate and sulfate-oxalate exchange. Next, two sulfated steroid hormones, estrone-3-sulfate (ES) and dehydroepiandrosterone sulfate (DHEAS) were tested as possible substrates. In sat-1-expressing oocytes [3H]ES uptake was not detectable. To test for ES-sulfate exchange, sat-1-expressing oocytes were injected with ES. However, subsequent [35S]sulfate uptake was not enhanced. DHEAS was neither taken up by sat-1 nor was DHEAS able to inhibit sulfate uptake. Our data indicate that sat-1 does not translocate sulfated steroid hormones. ES and DHEAS transport seems to be restricted to Oatp2, and sat-1 contributes only to sulfate homeostasis.