Characterisation of creatinine secretion across monolayers of mouse proximal tubule cells

The Renal clearance of creatinine is dependent upon the complex interplay between transport proteins at the basolateral and apical membranes of proximal tubule cells which act in concert to form an effective secretory mechanism. The role of OCT2 in the tubular uptake of creatinine is well established, but there is almost no information on the identity of the transporters involved in the apical exit step for creatinine secretion into the urine. The aim of this investigation was use primary cultures of mouse proximal tubule cell monolayers to identify the importance of individual transporters to the renal secretion of creatinine. To do this, steady state transepithelial fluxes of [ 14 C]creatinine and [ 3 H] mannitol were measured in cell monolayers grown on permeable filter supports. Results are expressed as mean ± SEM. For creatinine, the basolateral to apical flux (J ba ) was ~2 fold greater the apical to baolateral flux (J ab ) resulting in a net secretion (J net ) of creatinine across the monolayer (1.2±0.35 nmole/cm 2 /hr, P<0.001). Creatinine fluxes were inhibited by a range of organic cations and decynium‐22 at the basolateral membrane. Importantly the net secretion of creatinine was abolished in the presence of either verapamil or vinblastine (10μM) at the apical membrane face suggesting that the apical efflux of creatinine was mediated by MDR1 and/or MRP2. These data suggest that primary cultures of mouse tubule cells will prove an important model with which to gain understanding of creatinine secretion in an intact system.