TY - JOUR T1 - Identification and Characterization of Efflux Transporters that Modulate the Subtoxic Disposition of Diclofenac and its Metabolites JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.119.086603 SP - dmd.119.086603 AU - Renato J Scialis AU - Lauren M Aleksunes AU - Ivan L Csanaky AU - Curtis D Klaassen AU - Jose E Manautou Y1 - 2019/01/01 UR - http://dmd.aspetjournals.org/content/early/2019/08/09/dmd.119.086603.abstract N2 - In the present work, in vivo transporter knockout (KO) mouse models were used to characterize the disposition of diclofenac (DCF) and its primary metabolites following a single sub-toxic dose in mice lacking breast cancer resistance protein (Bcrp) or multidrug resistance-associated protein (Mrp)3. The results indicate that Bcrp acts a canalicular efflux mediator for DCF as wild-type (WT) mice had biliary excretion values that were 2.2- to 2.6-fold greater than Bcrp KO mice, though DCF plasma levels were not affected. The loss of Bcrp resulted in a 1.8- to 3.2-fold increase of diclofenac acyl glucuronide (DCF-AG) plasma concentrations in KO animals compared to WT mice, while the biliary excretion of DCF-AG increased 1.4-fold in WT versus KO mice. Furthermore, Mrp3 was found to mediate the basolateral transport of DCF-AG, but not DCF or 4ʹ-hydroxy diclofenac. WT mice had DCF-AG plasma concentrations 7.0- to 8.6-fold higher than Mrp3 KO animals, however there were no changes in biliary excretion of DCF-AG. Vesicular transport experiments with human MRP3 demonstrated that MRP3 is able to transport DCF-AG via a low and high affinity binding site. The low affinity MRP3 transport had a Vmax and Km of 170 pmol/min/mg and 98.2 μM, respectively, while the high affinity Vmax and Km parameters were estimated to be 71.9 pmol/min/mg and 1.78 μ;M, respectively. In summary, we offer evidence that the disposition of DCF-AG can be affected by both Bcrp and Mrp3, and these findings may be applicable to humans.SIGNIFICANCE STATEMENT We report that diclofenac was found to be a substrate of Bcrp but not Mrp3 using mouse transporter models. Using the same models, diclofenac acyl glucuronide was found to be a substrate of both Bcrp and Mrp3. Importantly, the loss of Mrp3 affects diclofenac acyl glucuronide plasma concentrations but has no apparent effect with respect to liver concentrations or biliary excretion rates. We also report that diclofenac acyl glucuronide as an apparent low affinity and high affinity for human MRP3 compared to human MRP2 for which a single binding site is considered operative. ER -