SLCO4C1 and Renal insufficiency: In studies with transgenic rats harboring human SLCO4C1, the decrease of uremic toxin (guanidino succinate, asymmetric dimethylarginine, and trans-aconitate) concentrations in plasma suggests that OATP4C1 may facilitate the excretion of uremic toxins in renal failure models and, by extension, in patients with chronic kidney disease.