Expression of cytochrome P450 mRNAs in the colon and the rectum in normal human subjects.

The expression of mRNA for three isozymes of cytochrome P450, CYP1A1, 1A2 and 3A3, was examined in biopsied samples of colon and rectum from five healthy subjects. Using RT-PCR, it was possible to detect the three CYP mRNA species at both sites in all samples examined. The expression of each CYP mRNA was site-specific in that rectum had higher levels of CYP1A1 mRNA than colon, while colon had higher levels of CYP3A3 mRNA than in rectum. In contrast, there was no consistent trend in CYP1A2 mRNA expression between the two sites. Variability of alimentary CYP expression may contribute to individual differences in susceptibility to carcinogens and/or drugs.