In vitro effects of estradiol on pituitary GH-immunoreactive cells.

In order to determine whether estradiol modulates the proliferation and activity of somatotrophic cells in vitro, a study of GH-immunoreactive cells was carried out in pituitary monolayer cultures obtained from male adult rats treated with 10(-6)M estradiol for 3 hours. Cellular activity was evaluated in a morphometric study of GH-immunoreactive cells. The proliferation rate was determined by double immunostaining for GH and PCNA (proliferating cellular nuclear antigen). The results were compared to those obtained from control dishes. Estradiol was seen to increase the cellular (p < 0.05), nuclear (p < 0.01) and cytoplasmic areas (p < 0.05). Estradiol decreased the percentage of proliferating GH-immunoreactive cells (p < 0.05) and the nuclear density of somatotrophs (p < 0.05) when all cells present in the dishes were considered. However, when only GH-immunoreactive cells were considered, estradiol increased the proliferation rate of these cells (p < 0.05). Overall, our results suggest that, in vitro, estradiol stimulates the cellular activity and proliferation of GH-immunoreactive cells in the rat.