Introduction: Angiogenesis is controlled by series of cellular interactions which are mediated by cell surface glycoconjugates terminal sugars. The aim of this study was to investigate the distribution and changes of the cell surface terminal sugars during hypothalamo– pituitary portal (HPP) system angiogenesis in rat embryos.

  Methods: In this study, 70 N-mary rat fetuses (10-20 gestational days) were used by lectin histochemichal technique as a tool to study distribution of the glycoconjugates and their changes during HPP system angiogenesis. All paraffin sections were incubated with different HRP- lectins from Vicica villosa (VVA), Glycine max (SBA) and Wistaria floribunda (WFA) specific for terminal sugars D-Gal, α, ß-D-GalNAc and D- GalNAc of complex glycoconjugates, respectively. On the basis of staining intensity, the sections were graded and nonparametric statistical test was used to compare differences between samples.

  Results: The results demonstrated that some cells around Rathke’s pouch reacted with VVA from day 13 and increased to day 14 and then decreased afterward, significantly (P<0.05). Some cells around Rathke’s pouch reacted with SBA from day 14 to day 18 and then decreased afterward (P<0.05). Many cells around Rathke’s pouch reacted with WFA from day 13 and increased on days day 14 and day 15 (P<0.05), then decreased with developmental advancement.

  Conclusion: Our findings indicated that the distribution and changes of glycoconjugates with terminal sugars D-Gal, α, ß-D-GalNAc and D- GalNAc were regulated spatiotemporally and might play critical role (s) in cell interactions and tissue differentiations such as angiogenesis during embryonic development.

  Keywords: Hypothalamo – hypophyseal portal system, glycoconjugates, lectin, rat.

  Hakim 2005 8(1) 52-59.