Estrogen increases the release of epidermal growth factor from individual pituitary cells in female rats

Rat mixed anterior pituitary cells from cycling females were microscopically demonstrated to produce epidermal growth factor (EGF), in culture, using a reverse hemolytic plaque assay. Anterior pituitary cells of proestrous female rats secrete more EGF than those of metestrous rats, as evaluated by the mean area and the percentage of EGF plaque-forming cells. Estradiol-17 beta (10 nM) treatment of metestrous culture for 24 h increased significantly the size of EGF plaque-forming cells (from 1290 +/- 58 to 2566 +/- 57 microns 2, P < 0.01) and the percentage of EGF plaque-forming cells (from 20.57 to 28.19%; P < 0.01) to a level as high as observed in proestrous cultures (basal mean area 2171 +/- 157 microns 2, and basal percentage of EGF plaque-forming cells 22.71%). These results suggest that the hormonal status of female rats influences EGF secretion in the anterior pituitary gland and that estradiol is implicated in this phenomenon.