Effect of estrogen and FGF-2 interaction on lactotroph cell proliferation mediated by membrane-initiated signaling

SOSA LILIANA DEL VALLE; GUTIÉRREZ SILVINA; PETITI JUAN PABLO;VACA, ALICIA MALDRE; DE PAUL ANA LUCÍA; TORRES ALICIA

Florencia

Congreso; 15th International and 14th European Congress of Endocrinology; 2012

Estradiol (E2) may directly interact with growth factors stimulating cell proliferation and differentiation. Previously, we have demonstrated that E2 through membrane estrogen receptor alpha (mERa) modulates the lactotroph cell population which exhibit noticeable changes in the pituitary gland. The aim of this study was to analyze the mERa 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 10nM of E2, E2 membrane-impermeable conjugated (E2BSA), PPT (ERa agonist), DPN (ERb antagonist) alone or combined with FGF-2 (0.6nM) for 30min or 4h. The lactotroph cell number was quantified by BrdU/PRL and PKCα andε; phosphorylated (p) and total Akt or ERK1/2, and ß-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 4h, being this effect blocked by ICI 182780 or PD98059 pre-treatment. The subcellular distribution of PKCa 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 PKCe translocation to lactotroph plasma membrane that was accompanied with a significant increase of PKCe expression after 4h. 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 mERa and the activation of PKCe/ERK1/2. This regulatory effect could participate in the homeostasis of pituitary cell populations.