METABOLISM OF [H-3] NORADRENALINE BY UMBILICAL ARTERIES AND PLACENTALBED TISSUE OBTAINED FROM NORMOTENSIVE AND PREECLAMPTIC HUMAN PREGNANCIES

Objective: To ascertain if the catecholamine content of placental bed tissue as well as the capacity of umbilical arteries and placental bed tissue to take up and metabolize [H-3]noradrenaline are different und er conditions of normotensive and preeclamptic pregnancy. Methods: Pla cental bed samples were obtained by biopsy at cesarean sections. Umbil ical arteries were dissected immediately after delivery. Noradrenaline , adrenaline, dopamine, and 3,4-dihydroxyphenylglycol (DOPEG) were mea sured in placental bed tissue by HPLC-ED. Umbilical arteries and place ntal bed slices were incubated with [H-3]noradrenaline, under control conditions or in the presence of inhibitors of uptake1 or uptake2. [H- 3]Noradrenaline and its metabolites were measured in tissues and incub ation fluids by scintillation counting after column chromatographic se paration. Results: Placental bed tissue had no detectable levels of no radrenaline, adrenaline, or dopamine. Relatively high levels of DOPEG were found in specimens from both normotensive and preeclamptic pregna ncies. Placental bed tissue showed a high capacity to take up (mainly through a mechanism that was sensitive to uptake2 blockers) and metabo lize [H-3]noradrenaline (through monoamine oxidase). Desipramine had n o significant effect on uptake and/or metabolism of [H-3]noradrenaline . Umbilical arteries formed a much smaller amount (25%) of metabolites than placental bed tissue, and uptake blockers had no significant eff ect on metabolite formation, In preeclampsia the capacity to take up a nd/or to deaminate [H-3]noradrenaline to [H-3]DOPEG was significantly reduced in both umbilical arteries and placental bed tissue. Conclusio ns: Placental bed tissue seems to be devoid of adrenergic innervation in both normotension and in preeclampsia. This tissue has a high capac ity to take up and deaminate [H-3]noradrenaline. The capacity to take up and/or deaminate [H-3]noradrenaline to [H-3]DOPEG is significantly reduced in preeclampsia. The presence of high levels of endogenous DOP EG in placental bed tissue from preeclamptic pregnancies is compatible with high levels of circulating catecholamines in this situation.