Fluorescence localization of anti-pregnant rat kidney antibody and lectin binding analysis in exencephalic rat embryos.

We sought to determine the distribution of anti-pregnant rat kidney serum (ARKS) in fetuses that subsequently developed a form of neural tube defect (NTD). We produced exencephaly in rat embryos by injecting a rabbit anti-pregnant rat kidney serum into the peritoneal cavity of pregnant Wistar rats on day 7 of gestation; 71.1% (27/38) of the rat embryos developed this anomaly. Fluorescence immunohistochemical studies were performed to localize ARKS binding in the embryos. We also investigated the binding of two lectins, concanavalin A (ConA) and wheat germ agglutinin (WGA), to glycoconjugates on neuroepithelium during the process of neurulation in rat embryos injected with normal rabbit serum (NRS) and ARKS. We found for the first time that ARKS directly affected the neural tube during neurulation. Intense fluorescence was observed on the luminal side of the neuroepithelium in the intercellular region and on the basement membrane of the neural tube in embryos on day 9 of gestation (GD9). In GD21 embryos there was much more intense fluorescence in the extracellular matrix and the ependymal lining cells of the ventricles than in controls. The binding of the two lectins on the cell surface of the neuroepithelium during neurulation was different in rat embryos injected with ARKS than in normal embryos injected with NRS. These results support the idea that simple nonclosure and overgrowth constitute the mechanism of NTD. However, the lectinbinding data suggest that dysraphic states may be induced by cell-to-cell adhesive molecular failure.