[Development of the mono-oxygenase system. Implications in perinatal pharmacotoxicology (author's transl)].

The hepatic or extra-hepatic mono-oxygenase activities ensure the metabolism of exogenic hydrophobic substances (xenobiotics) and endogenic substances (steroids). These substances easily cross the placenta ; it is of primary importance to know perfectly their possible transformation at the level of the foetus together with their excretion from the foetal compartment. We summarise here the data in the literature which describe the development of the mono-oxygenase system and the microsomal enzyme activities of phase II (epoxide hydrolase and UDP-glucuronosyl-transferase) both in the laboratory animal and in the human foetus. The influence of various factors (exogenic inducers, endogenic hormones) on the development of these activities is also reported. Although a conclusion is difficult concerning the present state of our knowledge, the main pharmacotoxicological consequences of the development of mono-oxygenasic activities are considered.