title: Ethanol-mediated transplacental induction of CYP2E1 in fetal rat liver.
abstract: We examined the potential for the widely consumed xenobiotic ethanol to transplacentally induce fetal rat CYP2E1. Throughout gestation, rat dams were fed a liquid diet containing 5% ethanol or two separate control diets. At 2 days before term, the dams were killed, and maternal and embryonic tissues were collected. Immunoblot analysis of microsomes from fetal liver, placenta and maternal brain revealed a band that comigrated with adult liver CYP2E1. The identity of the immunoreactive protein in placenta, brain and fetal liver was substantiated as CYP2E1 through restriction enzyme digestion of a reverse transcription-polymerase chain reaction product. Quantification of immunoblots containing microsomes from maternal and fetal liver of ethanol-treated dams displayed a 1.4- and 2.4-fold increase in CYP2E1, respectively, compared with microsomes from pair-fed controls. Chlorzoxazone and low substrate concentrations of N-nitrosodimethylamine were used as metabolic probes for CYP2E1. The rate of chlorzoxazone metabolism by maternal hepatic microsomes from dams fed the 5% ethanol diet was 2.6-fold greater than that of controls. Conversely, a negligible increase was observed in the rate of metabolism by hepatic microsomes from ethanol-exposed fetuses compared with pair-fed animals. When N-nitrosodimethylamine demethylation was examined, these same fetal samples exhibited greater rates of activity (1.5-fold) compared with microsomes from control animals. However, this increase was not as great as expected considering the 2.4-fold increase in CYP2E1 protein. Collectively, fetuses exposed to a 5% ethanol diet throughout gestation exhibited transplacental induction of an hepatic CYP2E1 that may possess different catalytic properties from the analogous adult enzyme.
authors.affiliation: University of New Mexico, College of Pharmacy, Albuquerque, USA. scarpen@agi.org
authors.forename: S P
authors.initials: SP
authors.lastname: Carpenter
authors.forename: D D
authors.initials: DD
authors.lastname: Savage
authors.forename: E D
authors.initials: ED
authors.lastname: Schultz
authors.forename: J L
authors.initials: JL
authors.lastname: Raucy
mesh_terms: D000818:Animals; D002384:Catalysis; D002753:Chlorzoxazone / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis* / Q000378:metabolism; D004790:Enzyme Induction; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000201:enzymology; D007150:Immunohistochemistry; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D009603:Nitroso Compounds / Q000378:metabolism; D010920:Placenta / Q000187:drug effects*; D011247:Pregnancy; D051381:Rats
chemical_list: D009603:Nitroso Compounds; C008651:4-nitrosodimethylaniline; D000431:Ethanol; D019392:Cytochrome P-450 CYP2E1; D002753:Chlorzoxazone