The effect of simultaneous versus sequential estradiol and progesterone treatments on prolactin production in monkey pituitary cell cultures

Dispersed monkey pituitary cells were cultured in serum-free medium and on extracellular matrix for 30 days. After 10–14 days with only insulin, transferrin, and selenium (ITS), the addition of estradiol (E) significantly increased PRL secretion compared to that in vehicle-treated controls. Simultaneous addition of E plus progesterone (P) increased PRL secretion similarly to E alone. PRL secretion in cultures treated with E plus P after 10 days induction by E was also similar to that in cultures maintained continuously in E. PRL secretion declined in wells switched from E to P and in wells switched from E back to vehicle, relative to that in wells maintained continuously in E. Estrogen receptors (ER) were detected in whole pituitary tissue and in serum-free pituitary cultures with a monoclonal antiestrogen receptor antibody (H222) in a sucrose density gradient shift assay. Immunocytochemical staining for ER with the same antibody also showed positive cell nuclei in serum-free pituitary cultures. In summary, ER are maintained in monkey pituitary cells during tissue culture, and PRL production can be further increased by E treatment after long term serum-free culture. Neither simultaneous nor sequential E plus P treatment alters PRL secretion compared to E alone.