Metabolism of 3H-dopamine by human chorioamnion in vitro

Previous investigation has demonstrated biologically significant concentrations of catecholamines in amniotic fluid, which increase with gestation. The half life, metabolic clearance rate, and metabolic fate of these hormones in the amniotic compartment are yet to be established. This study was undertaken to demonstrate the ability of human chorioamnion to metabolize dopamine in vitro. Incubation experiments demonstrated that 3H-dopamine is rapidly metabolized to dihydroxyphenylacetic acid, 3-methoxy,4-hydroxyphenylacetic acid, and 3-methoxy,4-hydroxyphenylethanol—all products of monoamine oxidase. No significant 3-methoxytyramine, a catechol-o-methyltransferase product, was observed. Incubation experiments with pargyline, a monoamine oxidase inhibitor, resulted in significant reduction in 3H-dopamine metabolism. Catecholamines and their interaction with prostaglandin synthesis have been theorized to be a fetal signal for the initiation of parturition. The ability of chorioamnion to metabolize catecholamines could, therefore, provide another control mechanism by which fetal catecholamines are modulated.