Transference of monoamines in amniotic fluid across the fetal membrane

The role of monoamine oxidase (MAO) on fetal membranes in transference of catecholamines (CAs) was studied. Fetal membranes were obtained from pregnant women at the time of normal delivery (ND) or elective Cesarean section (CS) at term. Intact fetal membranes were placed in a chamber and cultured under sterile conditions. 14 C-5-hydroxytryptamine (5-HT) was added to the fetal side of the fetal membranes. After incubation, both sides of the media were collected and the concentration of radiolabeled 5-HT and its metabolites was determined. In the CS group, the radioactivity on the maternal side increased time-dependently up to 12 hr. Following a 2-hr incubation, the transferred radioactivity on the maternal side did not differ significantly between the ND and CS groups. However, the radioactivity of the 5-HT metabolite in the ND group was significantly higher than that of the CS group (p<0.05). MAO activity in fetal membranes appears to control the amniotic CA influx into the myometrium. Furthermore, MAO activity in fetal membranes may play a protective role in the transference of monoamines for uterine contraction during pregnancy via fetal membranes due to appropriate uterine contraction during labor.