Epidermal growth factor induces a sexually dimorphic proliferative response of lactotroph cells through protein kinase C-ERK1/2-Pit-1 in vitro.

Lactotroph cells display morphological and functional heterogeneity, a feature which is closely related to the oestrogenic environment. In this study, we focused on sex-related differences linked to the proliferative and secretory responses of lactotrophs exposed to EGF in vitro. Furthermore, we addressed the involvement of the PKCε/ERK1/2 signalling pathway and the contribution of Pit-1 in the EGF actions in primary pituitary cultures from male and female rats. EGF promoted a differential proliferative activity on PRL cells, which was closely associated to the sex, as revealed by the uptake of bromodeoxyuridine (BrdU). In females, the mitogenic activity was up to nine times greater, whereas in males, the number of BrdU-labelled PRL cells was only doubled compared to control. However, in both models, EGF had a similar effectiveness in promoting PRL secretion. EGF also induced a significant increase in the PKCε, P -ERK 1/2, and Pit-1 protein levels, which were higher in females than in males. Pre-incubation with BIM blocked EGF-induced ERK 1/2 activation and Pit-1 expression. These results suggest a sexually dimorphic response of lactotroph cells to the proliferative effects of EGF, with the PKCε/ERK1/2 Pit-1 pathway being involved in this action.