DIVERSITY OF PITUITARY-CELLS IN PRIMARY-CELL CULTURE - AN IMMUNOCYTOCHEMICAL STUDY

In cell cultures of dispersed rat anterior pituitary, the specific ide ntification of each cell type based on their staining properties and t he ultrastructural features of secretory granules has proved to be unr eliable. The existence of pituitary cell subtypes and the striking rem odelling of the cell surface and intracellular organelles, further com plicate the specific identification of pituitary cell populations. An immunocytochemical study of dissociated pituitary cells in culture was carried out to identify the cellular hormonal content by applying spe cific antibodies against prolactin (PRL), and growth (GH), luteinizing (LH beta), adrenocorticotrophic (ACTH) and thyrotrophic (TSH) hormone s. Specifically bound IgG was exposed by the electron microscope with protein A-gold complex. Typical lactotrophs, somatotrophs and gonadotr ophs are easily recognized because they retain the main features descr ibed in the pituitary tissue in situ. Other undefined groups of cells bearing small or medium round secretory granules can be identified by immunocytochemistry as PRL, GH or TSH producing cells. The latter tech nique was critical for the characterization of the hormonal content of secretory granules, the shape, size, electron density and cytoplasmic distribution of which differ substantially from those described in th e intact gland. Cells displaying rare small oval or sharp pointed secr etory granules were identified as gonadotrophs with anti-LH beta, whil e corticotrophs showed granules with irregular profiles not previously reported in the gland. These remarkable morphological changes appear to be related to the interruption of the now of hypothalamic hormones and the disruption of structural and paracrine interrelationships. Thi s investigation reveals that immunocytochemistry is essential for the specific recognition of the various pituitary cell types, and particul arly of atypical cells exhibiting morphological features not found in the pituitary gland in situ.