Parathion transfer and acetylcholinesterase activity in an in-vitro perfused term human placenta

Organophosphate transport through the placenta was investigated in an in-vitro placental perfusion system. The system consisted of maternal and fetal reservoirs in which Krebs Ringer bicarbonate buffer with heparin, albumin and glucose was circulated at a constant pH, temperature and pO2. Parathion was analysed by means of gas chromatography with a N-P detector. 14C Antipyrine, a lipid soluble salt, was used as an internal standard, which allowed for the difference in placental size and permeability. A certain amount of parathion passed the placenta and reached the fetal compartment. Glucose consumption was not influenced by the introduction of parathion; neither was the water content of the placental tissue. Acetylcholinesterase activity in placental tissue decreased 50%. The amount of parathion transferred was not negligible and could have caused damage to a fetus.