Metabolism of the human placenta perfused in vitro: glucose transfer and utilization, O2 consumption, lactate and ammonia production.

Oxygen consumption, glucose transfer and utilization, and lactate and ammonia release were studied in the human full term placenta using an in vitro perfusion technique. D-Glucose was the only substrate added to the perfusion fluid. On the maternal side, oxygen and glucose were taken up at a constant rate during perfusion. On the fetal side, a lower oxygen uptake was observed. Glucose was steadily released into the fetal perfusate as a result of the downhill concentration gradient established between maternal and fetal circulations. By contrast, lactate and ammonia release took place only into the maternal circulation and decreased rapidly during perfusion. No significant change in tissue glucose content was observed between the onset and the end of the experiment. Placental lactate and ammonia concentrations were shown to diminish significantly during perfusion.