DETECTION OF CYTOCHROME-P450 GENE-EXPRESSION IN HUMAN PLACENTA IN FIRST-TRIMESTER OF PREGNANCY

Human first-trimester placentas were screened for the expression of xe nobiotic-metabolizing cytochrome P450 (CYP) genes. mRNAs of CYP1A1, CY P1A2, CYP2C, CYP2D6, CYP2E1, CYPZF1, CYP3A4, CYP3A5, CYP3A7, and CYP4B 1 were identified by reverse transcriptase-polymerase chain reaction ( RT-PCR) in at least some of the six placental samples studied. CYP2A a nd CYP2B messages were absent in all samples. The level of all of thes e CYP mRNAs was lower compared to the corresponding levels in liver or lung. The catalytic activity marker (7-ethoxyresorufin O-deethylase) was inducible in the placentas by maternal cigarette smoking. Thus, th e regulatory system of placental CYP1A1, mediated by the Ah-receptor, appears to be developed as early as the first trimester of pregnancy. Three immunoreactive bands from placental microsomes were detected by an antihuman CYP3A4 antibody, but no functional activity of CYP3A enzy mes could be detected. These results show that placental tissue during the first trimester of pregnancy has the potential of expressing seve ral CYP genes, and forms a basis for subsequent analysis of these form s at the protein and functional level.