17â-Estradiol modulates the prolactin secretion induced by TRH through membrane estrogen receptors via PI3K/Akt in female rat anterior pituitary cell culture

SOSA LDV; GUTIéRREZ S; PETITI JP; PALMERI CM; MASCANFRONI ID; SOAJE M; DE PAUL AL; TORRES AI

American Journal of Physiology and Metabolism

The American Physiological Society

Lugar: Bethesda; Año: 2012 vol. 302 p. 1189 - 1197

1522-1555

Considering that estradiol is a major modulator of prolactin (PRL) secretion, the aim of the present study was to analyze the role of membrane estradiol receptor-_ (mER_) in the regulatory effect of this hormone on the PRL secretion induced by thyrotropin-releasing hormone (TRH) by focusing on the phosphatidylinositol 3-kinase (PI3K)/ protein kinase B (Akt) pathway activation. Anterior pituitary cell cultures from female rats were treated with 17_-estradiol (E2, 10 nM) and its membrane-impermeable conjugated estradiol (E2-BSA, 10 nM) alone or coincubated with TRH (10 nM) for 30 min, with PRL levels being determined by RIA. Although E2, E2-BSA, TRH, and E2/TRH differentially increased the PRL secretion, the highest levels were achieved with E2-BSA/TRH. ICI-182,780 did not modify the TRH-induced PRL release but significantly inhibited the PRL secretion promoted by E2 or E2-BSA alone or in coincubation with TRH. The PI3K inhibitors LY-294002 and wortmannin partially inhibited the PRL release induced by E2-BSA, TRH, and E2/TRH and totally inhibited the PRL levels stimulated by E2-BSA/TRH, suggesting that the mER mediated the cooperative effect of E2 on TRH-induced PRL release through the PI3K pathway. Also, the involvement of this kinase was supported by the translocation of its regulatory subunit p85_ from the cytoplasm to the plasma membrane in the lactotroph cells treated with E2-BSA and TRH alone or in coincubation. A significant increase of phosphorylated Akt was induced by E2-BSA/ TRH. Finally, the changes of ER_ expression in the plasmalemma of pituitary cells were examined by confocal microscopy and flow cytometry, which revealed that the mobilization of intracellular ER_ to the plasma membrane of lactotroph cells was only induced by E2. These finding showed that E2 may act as a modulator of the secretory response of lactotrophs induced by TRH through mER, with the contribution by PI3K/Akt pathway activation providing a new insight into the mechanisms underlying the nongenomic action of E2 in the pituitary.