Cytochrome P450 3As Gene Expression and Testosterone 6β-Hydroxylase Activity in Human Fetal Membranes and Placenta at Full Term

Expression levels of cytochrome P450 (CYP) 3A4, CYP3A5 and CYP3A7 mRNAs in placentas and fetal membranes, which were split into amnion and chorion leave attached decidua (chorion/decidua), obtained from pregnant women with normal delivery (5 subjects) and Caesarean section (15 subjects) were determined. These CYP3A mRNAs were also expressed in amnion and chorion/decidua together with placenta, although the expression level of these mRNAs was strikingly different between subjects. The expression level of the CYP3A4 mRNA in the placenta was about 2-fold higher than those in amnion and chorion/decidua. On the other hand, the expression levels of CYP3A5 and CYP3A7 mRNAs were highest in chorion/decidua. The immunologically related protein(s) with CYP3A7 was detected in all tissues examined. Testosterone 6β-hydroxylase activity in homogenate of human placenta, amnion and chorion/decidua were 26.6, 3.7 and 4.6pmol/h/mg protein, respectively. These results suggest that CYP3As in fetal membranes have the metabolic function to protect the fetus from exposure to drugs. Cytochrome P450 represent a superfamily of heme proteins that play a critical role in the oxidative metabolism of xenobiotics and endogenous substances, and there are several isoforms.