Estrogen receptors are involved in luteinizing hormone (LH) pulsatility during pregnancy in the vizcacha, Lagostomus maximus.

HALPERIN J; CORSO MC; INSERRA PIF; PROIETTO S; VITULLO AD; DI GIORGIO NP; DORFMAN VB; SCHMIDT AR; LUX-LANTOS V; YANKELEVICH L; CORTASA SA; CHARIF SE

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

The SouthAmerican plains vizcacha shows ovulatory aroundmid-gestationenabled by a hypothalamic-hypophyseal-ovarian axisactivitywith elevated levels of serum estradiol (E2) and gonadotropin-releasing hormone(GnRH). Considering that E2 is involved inhypophysealregulation, the aim was to study the action of E2 receptors(ER) onluteinizing hormone (LH) secretion in the vizcacha duringgestation.We used hypophyses of early- (EP), mid- (MP), andterm-pregnant(TP) vizcachas to study GnRH receptor (GnRHR),ER alpha(ERa), ER beta (ERb), and LH expression by Western-blotandimmunohistochemistry, and LH pulsatility by RIA (n=6 / group).In order toevaluate the action of ER on LH secretion, LH pulsatilitywas studiedin hypophyses of ovulating females incubated with ERaand ERbantagonists, or ERa and ERb agonists supplementation.Hypophyseswithout supplementation were used as control (CTL).ANOVAfollowed by Bonferroni was used to determine significant differencesamonggroups (p<0.05). A significant decrease in LH pulsatilitywasobserved in TP vs MP and EP, and this was concordantwithvariations in serum LH. Hypophyseal expression of GnRHR andERa showedsignificant increments at MP vs EP and TP. In addition,ERbexpression levels did not change during gestation. The colocalizationanalysis ofERa with GnRHR showed a decrease in MPvs EP andTP, whereas the colocalization of ERa with LH showedaconcordant increment with pregnancy progression. Regarding totheinvolvement of ER in LH secretion, LH pulsatility showed significantdecreasewith ERa or ERb specific agonists vs CTL whereasthecombination of both ER antagonists showed a decrement vsagonistseffects. These results suggest that ER would enable LHpulsatillityin the vizcacha at mid-gestation as result of a hypophysealsensibilizationto GnRH input. Moreover, LH secretion duringovulationmay require the action of both ERa or ERb isoforms. Fund.Científ. Felipe Fiorellino, PIP110/14, PICT1281/2014.Keywords:estrogen, hypophysis, vizcacha, LH, GnRH.