title: Placental monoamine oxidase content and inhibition: effect of enzyme inhibition on maternofetal transfer of noradrenaline (norepinephrine) in the human placenta in vitro.
abstract: The effect of monoamine oxidase (MAO) inhibition on maternofetal transfer of noradrenaline (NA) has been investigated in vitro using dual perfusion of isolated human placental lobules. As a first step, placental MAO content and its sensitivity to inhibition by pargyline were assessed in incubation studies of homogenates as well as during perfusion, taking rat liver as reference. Our results show that the human placenta, though it contains as great an enzyme activity as rat liver, was less sensitive to inhibition by pargyline than the latter. MAO inhibition by pargyline significantly reduced the NA clearance from maternal to fetal circulation. Thus the proportion of unmetabolized NA radioactivity in fetal venous samples decreased significantly after pargyline treatment. A concomitant rise in the proportion of mainly O-methylated metabolites was also observed. We speculate that the apparent activation of catechol-O-methyl transferase pathway, observed in our studies on MAO inhibition, may play an important role in limiting NA transfer towards the fetus in toxaemic pregnancies associated with the reduction in placental MAO.
mesh_terms: D000420:Albuterol / Q000378:metabolism; D000818:Animals; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008431:Maternal-Fetal Exchange / Q000187:drug effects; D008995:Monoamine Oxidase / Q000032:analysis*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D010293:Pargyline / Q000494:pharmacology; D010477:Perfusion; D010920:Placenta / Q000201:enzymology* / Q000378:metabolism; D011247:Pregnancy; D051381:Rats
chemical_list: D008996:Monoamine Oxidase Inhibitors; D010293:Pargyline; D008995:Monoamine Oxidase; D000420:Albuterol; D009638:Norepinephrine