Identification and responsiveness of prolactin-containing secretory granules in clonal rat mammotrophs

Clonal pituitary cells (2B8) derived from embryonic Rathke's pouch epithelium of Wistar-Imamichi rats established by Ishikawa et al. (1977) were used in this study. Late-passage 2B8 cells were found to contain small secretory granules which contained immunoreactive prolactin as demonstrated by electron microscopic immunocytochemistry. When 2B8 cells were incubated in the presence of various agents that are known to stimulate or inhibit prolactin secretion, the volume density of the secretory granules in the cytoplasm was shown to be altered.