Cytochromes P450 and MDR1 mRNA expression along the human gastrointestinal tract

Aim The aim of this study was to quantify the mRNA expression of three cytochromes P450 (CYP) and P‐glycoprotein (P‐gp) in the human gastrointestinal (GI) tract. Method Biopsies were obtained from gastric, duodenal, colonic and rectal mucosa during routine gastro‐colonoscopy in 27 patients. The biopsies were snap‐frozen in liquid nitrogen. Real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR) was used for the quantitative analyses of mRNA expressed by the CYP2E1, CYP3A4 and CYP3A5 genes, and the MDR1 gene coding for P‐gp protein. The mRNA expression of b‐actin was used as an internal standard for comparisons between samples. Results All CYP genes were expressed at all locations throughout the GI tract, although all showed substantial interindividual variation. CYP2E1 had the highest expression at all locations (P