IMMUNOCYTOCHEMICAL LOCALIZATION OF BASIC FIBROBLAST GROWTH-FACTOR IN THE RAT PITUITARY-GLAND

Immunohistochemical localization of basic fibroblast growth factor (bFGF) was studied in the rat pituitary gland at light and electron microscopic levels using a specific monoclonal antibody. In the anterior lobe, bFGF-immunoreactivity was found mostly in a cell population without secretory granules, which was identified as the folliculo-stellate (FS) cell by its ultrastructure and expression of S-100 protein. The subcellular localization of the immunoreactivity in FS cell was strictly nuclear. Besides the FS cell, a minor cell population containing small granules of 60-100 nm diameter, which seemed to represent immature endocrine cells, was immunostained in the nuclei with the anti-bFGF antibody. In the intermediate lobe, a subpopulation of the S-100 protein-positive cells lining the pituitary cleft was immunoreactive for bFGF. These results imply that the agranular cell types are the main producer and/or target of rat pituitary bFGF, and that bFGF may play a role in the differentiation of pituitary endocrine cells.