Metabolizing enzyme localization and activities in the first trimester human placenta: the effect of maternal and gestational age, smoking and alcohol consumption.

BACKGROUND The rationale for this study was to assess the expression, activity and localization of the enzymes uridine diphosphate glucuronosyltransferase (UGT), beta-glucuronidase, cytochrome P450 1A (CYP1A) and cytochrome P450 2E1 (CYP2E1) in first trimester human placenta and to gauge the effects of maternal variables on placental metabolism. METHODS CYP1A, CYP2E1, UGT and beta-glucuronidase activities were assessed in 25 placentas using ethoxyresorufin, chlorzoxazone, 4-methylumbelliferone and 4-methylumbelliferone glucuronide respectively. Protein expression and localization were detected by immunoblot and immunohistochemistry. All statistics were non-parametric. RESULTS UGT, beta-glucuronidase and CYP1A activities were detected in all placentas sampled; CYP2E1 was undetectable. CYP1A, UGT1A UGT2B proteins were detected in all placentas (n = 6) tested and CYP2E1 in 4/6 placentas sampled and were localized to the syncytium. UGT and CYP1A activities were significantly elevated in the placentas of mothers who smoked (P < 0.05 and P < 0.001 respectively) and were greatest in women who both smoked and drank alcohol (P < 0.05 and P < 0.01 respectively). Enzyme activities were significantly negatively correlated with gestational age (P < 0.05, r = 0.54, UGT) and maternal age respectively (P < 0.001, r = 0.63, CYP1A). beta-Glucuronidase activity did not differ with patient variables. CONCLUSIONS Metabolism of compounds by the human placenta in the first trimester may be affected by maternal and environmental factors altering the activity of constitutive metabolizing enzymes.