Developmental Changes of Amniotic Fluid Alpha‐Fetoprotein Subtractions in Early Gestation

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Abstract
Using both concanavalin A crossed‐line affinity immunoelectrophoresis and lentil lectin crossed‐line affinity immunoelectrophoresis, developmental changes of alpha‐fetoprotein (AFP) subfractions were studied in 11 samples of human amniotic fluid obtained between 43 and 121 days of gestation. In the amniotic fluid at 43 or 48 days of gestation, only subfractions produced by the yolk sac were evident. The initial appearance of the subfractions produced by the fetal liver was first detected at 51 days of gestation. Percentages of liver‐originated subfractions rose rapidly with gestational age and reached a level of 50% at 54 days of gestation. The subfractions produced by the yolk sac disappeared from the amniotic fluid at 121 days of gestation. These findings suggest that, in early gestation, the yolk sac is mainly responsible for the fetal AFP synthesis and that initiation of AFP production by the fetal liver takes place between 48 and 51 days of gestation. In the present study, attention was also given to the origin of four subfractions separated by the lentil lectin crossed‐line affinity immunoelectrophoresis.