Progesterone and estradiol modulate gonadotropin-releasing hormone effect over LH surge in the South American Plains Vizcacha, Lagostomus maximus.

PROIETTO S; SCHMIDT AR; DI GIORGIO NP ; DORFMAN VB; CORSO MC; INSERRA PIF; VITULLO A; CORTASA S; FEEHAN K; HALPERIN J

Mar del Plata

Congreso; Reunión Anual de Sociedades de Biociencias SAIC-SAFE-SAB-SAP; 2019

SAIC-SAFE-SAB-SAP

During estral cycle, massive release of pituitary luteinizing hormone (LH) is required for the ovulatory event to occur. This is regulated by gonadotropin-releasing hormone (GnRH) and the ovarian hormones estradiol (E2) and progesterone (P4). Ovarian P4 enhances the positive feedback of E2 on GnRH and finally in the LH surge, suggesting that this hormone is also involved in the release of LH. Vizcachas have shown reproductive axis activity during gestation with release of ovarian and hypothalamic hormones and an increased LH surgeat mid-pregnancy. The aim of this work was to determine the effects of E2 and P4 on GnRH receptor (GnRHR) and LH in the vizcacha. Ex vivo and in vivo approaches were developed: 1- Pituitaries of non-pregnant vizcachas were cultured underdifferent conditions: a) Buffer, b) E2, c) GnRH, d) GnRH+E2; n= 4/group. 2- Non-pregnant females were ovariectomized (OVX) and treated with E2 (OVX+E2, 5 ug/kg); n= 4/group. 3- Pituitaries of non-pregnant females were probed in a pulsatil assay under different conditions: a) Buffer, b) P4, c) P4+RU486(PR antagonist). LH release was measured by RIA, whereas pituitary GnRHR, ERalpha and PR expression was studied by immunohistochemistry and Western blot. A significant inductionof LH release was determined in the pituitary culturessupplemented with GnRH and E2 (p