Clearance and Disposition of Urea in the Perfused Human Placenta

Urea clearance and disposition is studied in perfused human placenta in vitro using a novel perfusion technique of isolated placental lobules. The results on urea clearance compare well with published reports. The study shows the suitability of urea as a reference marker in placental perfusion studies. It is concluded that urea could serve as an effective reference marker in preference to antipyrine in clearance studies of molecules with membrane-limited transfer.