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.