Transport and Metabolism of Serotonin in the human placenta from normal and severely pre-eclamptic pregnancies

We have attempted to elucidate the possible participation of serotonin as an etiological factor in pre-eclampsia. The transport of serotonin into vesicles from the maternal-facing brush border membrane was measured, as well as the metabolism induced by monoamine oxidase (MAO) in placental homogenate obtained from normal-term and severely pre-eclamptic placentas. Kinetic analysis of serotonin uptake by the placental brush border membrane of the syncytiotrophoblast between normally pregnant and severely pre-eclamptic subjects showed no significant difference (similar Vmax and Km values). However, the metabolism of serotonin was significantly higher in placental homogenate from normal pregnancies than in placentas from severely pre-eclamptic pregnancies. These findings suggest that the higher plasma-free serotonin levels observed in severe pre-eclampsia are mainly due to a reduction in MAO-A activity and not limited by the rate of serotonin uptake into the cells. (C) 2000 S. Karger AG, Basel.