Mucosal biotransformation rates in the small intestine of children.

Biotransformation of ingested xenobiotics is known to take place in the gastrointestinal mucosa of laboratory animals and adult humans as well as in the liver. We studied the activities of aryl hydrocarbon hydroxylase, epoxide hydrolase, and glutathione peroxidase in 242 peroral small intestinal biopsy samples of children aged eight months to 18 years: 201 with normal histology, 21 with partial villous atrophy, and 20 with severe villous atrophy. All these enzymes were detectable even in the youngest children. The aryl hydrocarbon hydroxylase activity was age dependent, while the other measured enzyme activities were not related to the age of the patients. The aryl hydrocarbon hydroxylase activity was not related to the mucosal histology, but the epoxide hydrolase and glutathione peroxidase activities were diminished in samples with severe villous atrophy as compared with normal mucosa. This suggests that small intestinal mucosa with villous atrophy may produce oxidated, reactive metabolites, but further metabolism into detoxication products is decreased. This may expose persons with mucosal atrophy to possible harmful effects of environmental xenobiotics entering the body even at low doses.