Placental biogenic amine transporters: In vivo function, regulation and pathobiological significance

The biogenic amine transporters are part of a large family of plasma membra ne transporters. These carriers mediate the re-uptake of neurotransmitters from the synaptic cleft and plasma compartments. Re-uptake process is inhib ited by drugs like cocaine, fluoxetine and tricyclic antidepressants. There are specific transporters for norepinephrine, epinephrine, dopamine and se rotonin. The placenta expresses the norepinephrine and serotonin transporte rs, which is unusual as they are otherwise expressed predominantly in neuro nal tissue. Fetal catecholamine clearance rate is higher than under any oth er physiological conditions and is mediated in large measure by the placent al transporters. The high intrauterine catecholamine secretion and clearanc e rates are part of the unique fetal neuroendocrine milieu. They condition the fetus to a high capacity for catecholamine secretion in the early postn atal period when elevated sympathoadrenal system activity is vital for post natal survival. Because of the prominent catecholamine clearance rate, the fetus is vulnerable to the adverse effects of re-uptake inhibitors. Underst anding the mechanisms of expression and regulation of placental biogenic am ine transporters is important to the pathobiology of fetal conditions assoc iated With elevated catecholamine levels or intrauterine exposure to uptake inhibitors like cocaine. (C) 1999 W. B. Saunders Company Ltd.