Immunohistochemical localization of vascular endothelial growth factor in the endocrine glands of the rat.

Vascular endothelial growth factor (VEGF) is a secreted polypeptide with specific effects on endothelial cell growth and vascular permeability. While previous studies have focused on the expression of VEGF associated with angiogenesis in tumor and embryonal tissues, little is known about the role of VEGF in normal adult tissues. In the present study, a specific antibody was used to study the immunohistochemical localization of VEGF in the entire body of normal adult rats. Intense to moderate immunoreactivities for VEGF were detected in some endocrine cell types, namely, the parafollicular cell of thyroid gland, B cell of endocrine pancreas, N cell of adrenal medulla and a minority of the thyrotrophs of the pituitary gland. A certain exocrine cell type, i.e., the surface mucous cell of stomach, was also immunoreactive for VEGF. At the ultrastructural level, VEGF immunoreactivity was localized exclusively in the secretory granules of all immunopositive endocrine and exocrine cells examined. The present study provided immunohistochemical evidence for the occurrence of VEGF in subsets of endocrine and exocrine cells of normal adult rats, suggesting that these secretory cells regulate local vascular permeability through a paracrine action of VEGF.