Hypophyseal estrogen receptors are involved in luteinizing hormone (LH) secretion during gestation in the South American plains vizcacha, Lagostomus maximus.

PROIETTO, SOFIA; YANKELEVICH, LORENA; CHARIF SE, INSERRA PIF, SCHMIDT AR, CORTASA S, CORSO ; DI GIORGIO NP, LUX-LANTOS V; HALPERIN, JULIA; ALFREDO DANIEL VITULLO; DORFMAN, VERÓNICA BERTA

Concon

Workshop; INTERNATIONAL WORKSHOP IN NEUROENDOCRINOLOGY (IWNE); 2017

IWNE

The South American plains vizcacha, Lagostomus maximus, is a caviomorph rodent native to Argentina. It shows peculiar reproductive features like pre-ovulatory follicle recruitment during pregnancy with an ovulatory process around mid-gestation. We have described hypothalamic-hypophyseal-ovarian (HHO) axis activity in the vizcacha during pregnancy with estradiol (E2), luteinizing hormone (LH), and gonadotropin-releasing hormone (GnRH) increases. Hypophysis is the central regulator of the HHO axis being E2 a key hormone involved in the regulation of its activity. The aim of this work was to study the action of E2 on LH secretion at mid-gestation in the vizcacha. We used early- (EP), mid- (MP), and term-pregnant (TP) vizcachas to study GnRH receptor (GnRHR), estrogen receptor alpha (ERα) and beta (ERβ), and LH expression by Western-blot and immunohistochemistry, and their co-localization by immnunofluorescence (n=6 per group). GnRH and LH pulsatilities were studied in all groups by incubation of hypothalamic and hypophyseal explants respectively, in Krebs-Ringer buffer, and the secretion of GnRH or LH evaluated in the incubation media by RIA (n=5 per group). ANOVA followed by Newman-Keuls Multiple Comparisons test was used to determine significant differences among groups (p<0.05). Significant variations were determined in the pulsatile frequencies of GnRH and LH during pregnancy. Significant increments were observed at MP related to EP, whereas GnRH pulsatility showed significant increase and LH pulsatility significant decrease at TP vs MP and EP. Those increments were concordant with variations in the total GnRH and LH mass delivered. Hypophyseal expression of GnRHR and ERα showed significant increments at MP related to EP and TP females (p<0.05), and exhibited a similar pattern to serum LH levels. However, hypophyseal content of LH did not vary throughout gestation. In addition, ERβ expression levels did not change during gestation. Confocal analysis of GnRHR with ERα and GnRHR with LH showed a higher colocalizating expression at MP. These results suggest that LH pulsatillity during pregnancy would be enabled by the increase of E2 at mid pregnancy that induces sensibilization of hypophysis to GnRH input stimulating GnRHR expression through ERα (Fundación Científica Felipe Fiorellino, CONICET-PIP110/14, and MINCyT-PICT1281/2014, Argentina).