Amniotic and maternal serum alpha-fetoprotein levels of rats with induced neural tube defects.

During the complete fetal period alpha-fetoprotein (AFP) was quantified in maternal sera and amniotic fluid from control, hypervitaminosis A and trypan blue treated normal rat fetuses, and from exencephalic and spina bifida aperta fetuses. The occurrence of histologic proven open neural tube defects was associated with amniotic fluid AFP levels that were much elevated over those of control and treated normal fetuses and those with closed neural tube defects at nearly the whole fetal period. In combining these results with the earlier reported morphologic data of the same rat fetuses as used in the present study, it is concluded that the elevation of amniotic AFP is caused by leakage of fetal serum through a disrupted and necrotic nervous tissue into the amniotic fluid. This experimental model of induced neural tube defects results in increase of amniotic fluid AFP levels similar to those found in human amniotic fluid in the presence of neural tube defects.