CONTRIBUTION OF OVARIAN FACTORS IN THE REPRODUCTIVE AXIS REACTIVATION OF PREGNANT VIZCACHAS

PROIETTO S, CORSO MC, CORTASA SA, SCHMIDT AR; DI GIORGIO NP, LUX-LANTOS V; VITULLO AD, DORFMAN VB; HALPERIN J

Mar del Plata

Congreso; Reunion Anual de Sociedades de Biociencias 2022; 2022

SAIC, SAI, FAIC, SAFIS

Unlike most mammals, pregnant vizcachas exhibit a reactivation ofthe hypothalamic-pituitary axis at mid-pregnancy showing gonadotropin and steroid hormones profiles similar to those describedduring the estrous cycle. In order to analyze the modulation of gonadotropin release during HHO axis reactivation, serum FSH and LHlevels; ovarian FSHR and LHR; steroidogenic enzymes as 3 β-HSD,17 β-HSD and CYP19A1; and inhibinβ-A were characterized by bothWestern-blot and immunohistochemistry. Serum estradiol and FSHlevels were measured by ELISA and serum LH by RIA. Pregnantvizcachas ovaries before and after the reactivation of the HHO axis(P2 and P3, respectively) were used. P2 females showed higherserum FSH levels and lower LH levels in comparison to P3 females.P3 ovaries presented significant changes in the analyzed markerscompare to P2, showing lower expression of FSHR and higher expression of inhibinβ-A and LHR. Inhibinβ-A immunolabeling wasmore noticeable in mature follicles than in corpora lutea. Regardingthe expression of steroidogenic enzymes, 3 β-HSD showed no differences, meanwhile a significantly higher expression of 17 β-HSDand lower expression of CYP19A1 were observed in ovaries of P2than that of P3. These results suggest that, during pregnancy, inhibinβ-A would control both the pituitary FSH secretion and the ovariansensitivity to this hormone by a negative feedback mechanism andby inhibition of its ovarian receptor respectively. Furthermore, theaugmented estradiol serum levels recorded in the P3 group wouldbe related to the key role of 17 β-HSD on androgens synthesisprior axis reactivation which would be converted into estradiol byCYP19A1 after reactivation. Moreover, this would cooperate in thenegative feedback on pituitary FSH release. These findings suggestthat inhibinβ-A and estradiol would exert negative feedback on FSHbut not on LH release during reactivation of the reproductive axis inpregnant vizcachas. FCFF, PIP11220200100036