Environmental influences on human foetal and placental xenobiotic metabolism

Summary The human foetus is more capable of metabolizing xenobiotics than foetuses of common laboratory animal species. However, xenobiotic metabolism in animal foetuses is inducible by the exposure of the mother to various inducers during late pregnancy. Xenobiotic metabolism in neonates is more easily inducible than in foetal animals. With respect to the human foetus at mid-pregnancy, the hepatic enzyme systems do not seem to be readily inducible by exogenous inducers, whereas the placental monooxygenase system is almost totally dependent on maternal cigarette smoking. In the human newborn, indirect evidence points to the possibility of induction by potential inducers. The ontogenetic development of xenobiotic metabolism is probably regulated by endogenous hormones. It is possible that environmental factors may affect these normal regulatory and imprinting phenomena and thus lead to permanent disturbances in xenobiotic metabolism.Presented at the International Workshop on Perinatal and Pediatric Aspects of Clinical Pharmacology, Heidelberg, Federal Republic of Germany, 27–29 February 1980