Persistence of cell types in monolayer cultures of dispersed cells from the pituitary pars distalis as revealed by immunohistochemistry

The objective was to study the fate of specific secretory cell types of the rat hypophysis when grown in primary monolayer cultures for periods ranging up to 32 days. The cells were identified immunohistochemically using peroxidase‐labeled antibody. Early in the culture period TSH‐cells were scarce and by 12 days they could no longer be identified. In most cultures LH‐cells were well stained and common for eight to 12 days, after which they underwent involution. Growth hormone cells were a prominent feature up to six days but by 12 days they were declining in number, size, and stainability; in contrast, prolactin cells proliferated and were large and intensely stained throughout the period of study, ultimately becoming the dominant secretory cell type. Corticotropic cells also continued throughout the period of study without regression. Thus drastic shifts occur with time in the relative proportions of cell types in monolayer cultures of rat pituitary cells.