E1b was the major Bcrp1 5′ UTR expressed in the mouse duodenum, jejunum and ileum accounting for at least 50% of the total Bcrp1 mRNA expression. Each data point in the figure is the average of duplicate PCR reactions from individual mice. Median values are represented by horizontal bar. E1u, E1a, E1b and E1c represent Bcrp1 alternative first exons 72kb, 58kb, 10kb and 5kb respectively upstream from the translation start site of Bcrp1 in Exon 2.