Localization of sialic acid-containing hormones in GTH cells and ACTH cells of the rat anterior pituitary

Summary The localization of sialic acid-containing substances in the rat anterior pituitary gland has been studied by light and electron microscopy, using a peroxidase-labeled lectin (Limulus polyphemus agglutinin: LPA) which binds specifically to sialic acid residues. LPA stains two types of anterior pituitary cells: (1) round or ovoid cells which are also positively stained with anti-hCG (GTH cell), and (2) small, stellate cells which are unstained with anti-hCG (ACTH cell). All of the LPA-positive cells can be distinguished from TSH cells which are identified by the use of anti-hTSH. On ultrathin sections directly stained with LPA using the postembedding method, the reaction is confined to the secretory granules in GTH cells, and ACTH cells. Of two types of secretory granules in GTH cells, the larger one is intensely stained, whereas the smaller type shows only weak staining with LPA. Since follicle-stimulating hormone (FSH) is known to have high sialic acid contents, the results suggest possible detection of FSH with a technique other than immunohistochemistry. Furthermore, if the sialic acid-containing substances in GTH cells represents FSH, then these results support the hypothesis that LH cells and FSH cells are one cell type.This research was supported by grants from the Ministry of Education of Japan