Relationship between Teratogenic Effects and Tissue Binding Pattern of Concanavalin A in Rat Embryos

ABSTRACT This study was conducted to examine the effects of concanavalin A (Con A) on rat neurulation. Con A was injected intravenously to pregnant rats at a single dose of 5, 10, or 20 mg/kg between gestational days (GD) 7.5 and 10.0, and the embryos were macroscopically examined on GD 11.5. Con A induced a high mortality rate, the treatment with 10 and 20 mg/kg on GD 9.5 was completely lethal. Con A caused a high incidence of neural tube defects (NTD), the incidence in the 10 mg/kg on GD 8.0 and 8.5 groups and in the 20 mg/kg on GD 8.0, 8.5 and 9.0 groups being significantly higher than that in the control group. Histological evaluation revealed that Con A inhibited neural tube expansion and altered neural crest cell shape. In the Con A-treated embryos, the stratified structure of the neuroepithelium was irregular and its extracellular space was expanded. In rat embryos from intact dams, the distribution of receptors for Con A was demonstrated histochemically on the cell surfaces around neurulation sites between GD 8.5 and 10.5, but not on GD 7.5. These findings indicate that Con A bound around the neurulation sites in rat embryos may disturb the cell-cell communication required to form the neural tube, resulting in NTD.