Modulatory effect of maternal serum on xenobiotic metabolizing activity of placental explants: modification by cigarette smoking.

The effect of sera from smoking and non-smoking women in the first trimester of pregnancy (8-11 weeks gestation) was tested on the activation of Phase I enzymes, aryl hydrocarbon hydroxylase and oestrogen hydroxylase, and Phase II enzymes, quinone reductase and catechol O-methyl transferase in explants prepared from first trimester placentae of smoking and non-smoking women. Addition of 10% sera for 16 h to explants from both smoking and non-smoking women significantly affected the activity of these enzymes although the effect varied according to the enzyme studied. Differences were also found in the response of smokers compared to controls. The 2% maternal serum or 10% male serum used as control had no effect on any enzyme activity. In conclusion, gestation age-matched maternal sera exert a significant effect upon the activity of placental xenobiotic metabolic enzymes in vitro early in pregnancy, supporting the view that the maternal environment may have a role in controlling placental metabolism which is altered by cigarette smoking.