Immunohistochemical identification of mouse adenohypophysial gonadotropes

Mouse pituitary gonadotropes were identified using immunohistochemical techniques with OsO4 single fixation. Most gonadotropes are immunostained with both LH beta and FSH antisera (FSH/LH gonadotropes), whereas a few gonadotropes are positive only for LH beta (LH gonadotropes). The former gonadotropes are large rounded or oval cells and contain two types of secretory granules: electron-dense smaller ones (about 100-200 nm in diameter) and electron-transparent larger ones (maximum diameter, about 400 nm) enclosed by a halo. The endoplasmic reticulum appears as a series of dilated sacs, and the Golgi apparatus is distinct. The mitochondria are found to have an electron-dense matrix throughout the cytoplasm, but are often concentrated in and around the region of the Golgi apparatus. These fine structural features are somewhat similar to those of the classical Barnes "FSH cell" The LH gonadotropes are polygonal cells of medium size. Small granules, as described above, are seen, but large granules are not. The Golgi apparatus is distinct, but small. The LH gonadotropes resemble neither the Barnes "LH cell" nor the Kurosumi-Oota "LH cell".