Endocrine Abstracts

Estradiol (E₂) may directly interact with growth factors stimulating cell proliferation and differentiation. Previously, we have demonstrated that E₂ through membrane estrogen receptor α (mERα) modulates the lactotroph cell population which exhibit noticeable changes in the pituitary gland. The aim of this study was to analyze the mERα contribution on lactotroph cell proliferation in response to E₂ and FGF-2 interaction evaluating the pathway involved in this effect. Pituitary cell cultures from Wistar female rats were treated with 10 nM of E₂, E₂ membrane-impermeable conjugated (E₂-BSA), PPT (ERα agonist), DPN (ERβ antagonist) alone or combined with FGF-2 (0.6 nM) for 30 min or 4 h. The lactotroph cell number was quantified by BrdU/PRL and PKCα and ε; phosphorylated (p) and total Akt or ERK1/2, and β-actin protein expression by western blot. In addition, MEK (PD98059) and ER (ICI 182780) inhibitors were used. The subcellular translocation of PKCα and ε was visualized by confocal microscopy. FGF receptors were identified by immuno-electron-microscopy. Statistical analysis: ANOVA-Tukey. In serum free condition, E₂, E₂-BSA, PPT, DPN or FGF-2 alone did not modify the lactotroph cell number, whereas E₂/FGF-2, E₂-BSA/FGF-2 or PPT/FGF-2 co-incubation significantly increased the mitogenic activity of these cells after 30 min or 4 h, being this effect blocked by ICI 182780 or PD98059 pre-treatment. The subcellular distribution of PKCα and pAkt did not exhibit any significant variation after treatments. However, the stimulation for 30 min with the combined treatments described above induced a remarkable increase of pERK1/2 and PKCε translocation to lactotroph plasma membrane that was accompanied with a significant increase of PKCε expression after 4 h. These findings show a cooperative effect of E₂ and FGF-2 on lactotroph proliferation triggered by signaling initiated at the plasma membrane with the contribution of mER α and the activation of PKCε/ERK1/2. This regulatory effect could participate in the homeostasis of pituitary cell populations.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.