Immunohistochemical Distribution of HNK-1 and N-CAM in Rat Embryos Treated with Bis-Diamine

Bis-diamine is known to induce congenital anomalies including cardiac defects, thymic hypoplasia and snout defects in rat embryos. Cardiovascular lesions consist of persistent truncus arteriosus, tetralogy of Fallot and aortic arch anomalies, which are often found in DiGeorge syndrome. In the the present study, we investigated effects of bisdiamine on cardiac neural crest cells, which may be important to the teratogenecity. A single dose of 200 mg bis-diamine was administered to pregnant rats at 10.5 embryonic day (ED). Immunohistochemical studies were performed on embryos at 11.5, 12.5 and 13.5 ED using anti-HNK-1 and anti-N-CAM antibodies. The embryos at 11.5 and 12.5 ED showed the similar distributional patterns of either HNK-1 or N-CAM positive cells in control and bis-diamine treated embryos. N-CAM immunoreactivities in the splanchnic mesoderm were quite weakly detectable in the bis-diamine treated embryos at 12.5 ED. Closure of the neural tube was delayed in the treated embryos at this period. Immunohistochemistry of the control embryos at 13.5 ED demonstrated a continuous chain of N-CAM expression between the neural plexus near the foregut and the fourth aortic arch, while no apparent continuity of N-CAM positive tissue was observed in the bis-diamine treated embryos. These findings suggested that bis-diamine reduced the amount of neural crest cells which appeared to participate in the aortic arch formation or conotruncal septation. The primary effect of bis-diamine in the induction of various congenital anomalies including cardiovascular malformations may be an inhibition of the normal development of the neural tube and neural crest.