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The transcription factor hepatocyte nuclear factor 1α (HNF1α) is involved in regulation of glucose metabolism and transport, and in the expression of several drug and bile acid metabolizing enzymes. Targeted disruption of the HNF1α gene results in decreased Cyp1a2, and Cyp2e1 expression, and increased Cyp4a1 and Cyp7a1 expression, suggesting these enzymes are HNF1α target genes. Since hepatic metabolism can be coordinately linked with drug and metabolite transport, this study aims to demonstrate whether HNF1α regulates expression of a variety of organic anion and cation transporters through utilization of an HNF1α-null mouse model. Expression of 32 transporters, including members of the Oat, Oatp, Oct, Mrp, Mdr, bile acid and sterolin families, was quantified in three different tissues: liver, kidney, and duodenum. The expression of 17 of 32 transporters was altered in liver, 21 of 32 in kidney, and 6 of 32 in duodenum of HNF1α-null mice. This includes many novel observations, including marked downregulation of Oats in kidney, as well as upregulation of many Mrp and Mdr family members in all three tissues. These data indicate that disruption of HNF1α causes a marked attenuation of several Oat and Oatp uptake transporters in liver and kidney, and increased expression of efflux transporters such as Mdrs and Mrps, thus suggesting that HNF1α is a central mediator in regulating hepatic, renal, and intestinal transporters.