17-beta estradiol and Thyrotrophin-releasing hormone interaction modulated prolactin secretion through membrane estrogen receptors via phosphoinositide 3-kinase/Akt.

SOSA, LV; GUTIERREZ, S.; PETITI, J. P.; PALMERI, C. M.; DE PAUL, A. L.; TORRES, A I

Buenos Aires

Congreso; III Iberoamerican Congress of Neuroimmunomodulation; 2009

Previously, we demonstrated that estradiol (E2) in interaction with TRH increased prolactin (PRL) secretion in lactotrophs. In the present study we investigated the participation of membrane and intracellular estrogen receptors (ER) and the involvement of PI3K/Akt pathway on E2 and TRH-stimulated PRL secretion. Primary pituitary cell cultures were treated with TRH (10nM), E2 (10nM) and its membrane-impermeable conjugated estradiol (E2-BSA, 10nM), alone or combined, for 30min. Specific PI3K inhibitors: LY294002 (10ìM) and wortmaninne (100nM) were used. PRL secretion was determinate by RIA, proteins expression (phosphorylated and total Akt and ERá) by western blot, and cell morphology was analyzed by electron microscopy. Statistical analysis: ANOVA-Tukey. Although E2, E2-BSA, TRH and E2/TRH increased the PRL secretion, the highest levels were reached with E2-BSA/TRH. Only E2-BSA/TRH enhanced the Akt phosphorilation. PI3K inhibitors partially inhibited the PRL secretion induced by TRH and E2/TRH and totally inhibited the PRL levels stimulated by E2-BSA/TRH. The expression of REá did not presented variations in the studied models. Lactotrophs incubated with E2-BSA/TRH exhibited scarce mature secretory granules, frequently in contact with the plasmalemma or in exocytosis process. These findings show that E2 in interaction with TRH, acting trough membrane ER, trigger PI3K/Akt signaling pathways increasing the PRL secretion.