Diversity of pituitary cells in primary cell culture. An immunocytochemical study.

In cell cultures of dispersed rat anterior pituitary, the specific identification of each cell type based on their staining properties and the ultrastructural features of secretory granules has proved to be unreliable. The existence of pituitary cell subtypes and the striking remodeling of the cell surface and intracellular organelles, further complicate 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 specific antibodies against prolactin (PRL), and growth (GH), luteinizing (LH beta), adrenocorticotrophic (ACTH) and thyrotrophic (TSH) hormones. Specifically bound IgG was exposed by the electron microscope with protein A-gold complex. Typical lactotrophs, somatotrophs and gonadotrophs are easily recognized because they retain the main features described 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 technique 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 the intact gland. Cells displaying rare small oval or sharp pointed secretory granules were identified as gonadotrophs with anti-LH beta, while 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 flow of hypothalamic hormones and the disruption of structural and paracrine interrelationships. This investigation reveals that immunocytochemistry is essential for the specific recognition of the various pituitary cell types, and particularly of atypical cells exhibiting morphological features not found in the pituitary gland in situ.