Stephanie van Hoppe

13 Introduction Figure 2 - Schematic representation of the expression sites of ABCB1 and ABCG2 and their transport direction in pharmacologically important organs. Shown is the transport direction of the ABCB1 and ABCG2 substrates in the kidney from the proximal tubular cells into the tubular lumen (i.e., towards the urine). In the intestines ABCB1 and ABCG2 transport their substrates from the enterocytes into the intestinal lumen (i.e., towards the feces), while in the brain these efflux transporters transport their substrates from the endothelial cells into the blood. In the liver ABCB1 and ABCG2 transport their substrates from the hepatocytes into the bile, i.e., towards the intestinal lumen. Figure 2 : Schematic representation of the expression sites of ABCB1 and ABCG2 and their transport direction in pharmacologically important organs. Shown is the transport direction of the ABCB1 and ABCG2 substrates in the kidney from the proximal tubular cells int the tubular lumen (i.e., towards the urine). In the intestines ABCB1 and ABCG2 transport their substrates from the enterocyt s into the intestinal lumen (i.e., towards the feces), while in the brain these efflux transporters transport their substrates from the endothelial cells into the blood. In the liver ABCB1 and ABCG2 transport their substrates from the hepatocytes into the bile, i.e., towards the intestinal lumen.