Yoshie Iwama

Two types of mammosomatotropes in mouse adenohypophysis

SummaryTwo types of mammosomatotropes (MS), the small-granule and vesicle-granule MS, were detected in mouse adenohypophysis by electron microscopy and immunohistochemistry. Both cell-types were immunoreactive to prolactin (PRL) and growth hormone (GH) antisera. The small-granule MS contained small, round, solid secretory granules about 100 nm in diameter, and were smaller than the classical GH and PRL cell-types. The vesicle-granule MS contained secretory granules like cored vesicles, and were larger than classical GH and PRL cells. Small-granule MS were immunoreactive to both PRL and GH antisera in the same region of the cell cytoplasm; the vesicle-granule MS, however, were immunoreactive to only PRL antiserum in most cytoplasmic areas, and a positive response to both PRL and GH antisera was confined to only certain small areas.

Identification of lactotropes (PRL cells), somatotropes (GH cells), corticotropes (ACTH cells) and thyrotropes (TSH cells) in the pituitary gland of the musk shrew, Suncus murinus L. (Insectivora), by immunohistochemistry.

By means of immunohistochemistry, lactotropes, somatotropes, corticotropes and thyrotropes in the pituitary of the male musk shrew, Suncus murinus L., were identified at the electron-microscopic level. Lactotropes were classified into three types: type I containing large (200-450 nm in diameter) round secretory granules, type II with medium-sized (150-250 nm in diameter) ones and type III with small (50-150 nm in diameter) ones. Somatotropes were also classified into type I somatotropes that contain large (450 nm in diameter) spherical secretory granules and type II somatotropes containing comparatively small (300 nm in diameter) round granules. Both type I and II somatotropes were small and sometimes contained rod-shaped granules. Corticotropes were round or oval cells with round secretory granules in various densities and sizes (150-500 nm in diameter) scattered all over the cytoplasm. Thyrotropes were angular or polyhedral cells containing electron-transparent round secretory granules (200-300 nm in diameter) and large irregularly shaped granules with a maximum diameter of about 1,500 nm. Each type of the cells may be distinguished by its respective ultrastructural characteristics alone without the aid of immunohistochemistry.

Classifications of Somatotropes, Lactotropes and Corticotropes in the Mouse Adenohypophysis with Immunohistochemistry

Somatotropes, lactotropes and corticotropes of adult male mice were identified with immunohistochemistry in the adenohypophysis fixed by OsO4 alone. Somatotropes were classified into type I somatotropes that contain large (350 nm in diameter) round secretory granules and type II somatotropes that contain small (100-200 nm in diameter) round secretory granules. Most somatotropes were type I somatotropes. Lactotropes were also classified into type I lactotropes that contain irregularly shaped secretory granules and type II lactotropes containing small (100-200 nm in diameter) round secretory granules. Corticotropes are irregular stellate or slender cells with little cytoplasm. They contain round solid secretory granules in various densities along the cell periphery. Most of these are low-density granules (200-300 nm in diameter) and a few are high-density granules (200-250 nm in diameter). These data were compared with the classical data of mouse adenohypophysial cells that were fixed in OsO4 alone and identified only by conventional electron microscopy.