Degradation of radiolabelled arginine vasopressin (125I-AVP) by the human placenta perfused in vitro.

The capacity of the human placenta to degrade 125I-labelled arginine vasopressin (125I-AVP) was studied in vitro using a dual circuit perfused lobule preparation. Seven placentas were perfused with the perfusate on the maternal side of the lobule containing 125I-AVP at the upper limit of the physiological range. On average, over a 30-min period, 48% of the 125I-AVP appeared to have been metabolized. With one exception, a patient whose labour was augmented with intravenous oxytocin, no 125I-AVP apparently crossed the placental lobule to the fetal circulation. These data indicate that the human placenta has a considerable capacity to degrade AVP.