Background/Aims: Organic anion transporter 1 (Oat1) and 3 (Oat3) are organic anion transporters that play critical roles in the body disposition of numerous clinically important drugs. We investigated the effects of acute uremia on the renal expression of Oat1 and Oat3 in three in vivo experimental models of acute kidney injury (AKI): induced by ischemia, by ureteral obstruction and by the administration of HgCl2 . We also evaluated the influence of urea in the expression of these transporters in proximal tubular cells suspensions. Methods: Membranes were isolated from kidneys of each experimental group and from cell suspensions incubated with different urea concentrations. Oat1 and Oat3 expressions were performed by immunoblotting. Results: A good correlation between uremia and the renal protein expression of Oat1 and Oat3 was observed in vivo. Moreover, the incubation of isolated proximal tubular cells with different concentrations of urea decreases protein expression of Oat1 and Oat3 in plasma membranes in a dose-dependent manner. Conclusion: The more severe the renal failure, the more important is the decrease in protein expression of the transporters in renal membranes where they are functional. The in vitro study demonstrates that urea accounts, at least in part, for the decreased expression of Oat1 and Oat3 in proximal tubule plasma membranes.Fil: Brandoni, Anabel. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Área Farmacología; Argentina.Fil: Brandoni, Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.Fil: Torres, Adriana Mónica. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Área Farmacología; Argentina.Fil: Torres, Adriana Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.