Albumin-bound kynurenic acid is an appropriate endogenous biomarker for assessment of the renal tubular OATs-MRP4 channel

E1: Protein-binding ratio of uremic toxins; E2: Uptake of uremic toxins in OAT1-, OAT3- and MRP4-overexpressing cells; E3: Validation of potential biomarkers of OATs and MRP4 in vitro; E4: Validation of potential biomarkers of OATs and MRP4 in vivo; E5: Transweel; E6: Specificity evaluation of potential biomarkers; E7: Sensitivity-CMPF; E8: Sensitivity-Kynurenic acid; E9: Sensitivity-N-(cinnamoyl); E10: Correlation analysis in human; E11: Kinetics of cefmetazole and biomarker in rats； E13: Serum level of biomarker in human.