Sensitivity of rat adenohypophyseal cells to estradiol and LHRH during long-term culture.

To determine possible effects of the time in culture on the responsiveness of the different pituitary cell types to estrogens, rat anterior pituitary cells were incubated up to 20 days in the presence or absence of 10 nM 17 beta-estradiol. Whereas spontaneous luteinizing hormone (LH) and thyroid-stimulating hormone (TSH) release decreased by 85-90%, follicle-stimulating hormone (FSH) and prolactin accumulation in medium were only 50% decreased after 20 days in culture, thus suggesting that the secretion of FSH and prolactin is less dependent on extrinsic stimulatory factors. Estradiol increased spontaneous LH release and its responsiveness to luteinizing hormone-releasing hormone (LH-RH) up to day 16 in culture, whereas the stimulatory effect of the estrogen on FSH secretion was significant only up to day 6. The stimulatory effect of estradiol on basal TSH release was seen up to day 8 in culture, whereas that on spontaneous prolactin release increased progressively after day 8 in culture up to the last time interval studied (20 days). As revealed by immunocytochemistry, the stimulatory effect of estradiol was not due to changes of cell growth.