Characterization of enzymes of catecholamine synthesis and metabolism in human fetal membranes at birth.

We looked for the presence of the enzymes monoamine oxidase, catechol-O-methyltransferase, and phenylethanolamine-N-methyltransferase in human fetal membranes at term. The activity of all three enzymes was detected via highly sensitive and selective radiometric enzyme assays. The most novel finding was the extremely high level of monoamine oxidase activity in the chorion compared with that in the amnion. The other enzyme of catecholamine metabolism, catechol-O-methyltransferase, did not show any difference in activity between the two layers. In addition, we observed that the enzyme phenylethanolamine-N-methyltransferase, which is primarily located in the adrenal medulla, was also present in appreciable levels in the two layers of fetal membranes. These results suggest that fetal membranes, like the placenta, possess the enzymatic machinery to metabolize catecholamines and have the capacity to synthesize epinephrine.