Apoptosis and expression of estrogen receptors in pituitary of male viscachas during the annual reproductive cycle

GABRIELA ROSALES; FABIÁN MOHAMED; VERÓNICA FILIPPA

Virtual

Congreso; XXXIX Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2021

Sociedad de Biología de Cuyo

Estrogens through their specific receptors (RE and ) act as modulators of cell renewal in the pituitary gland, being mediators in the processes of proliferation and cell death. The aim of this work was to localize and quantify the apoptotic cells and the expression of RE in different regions of pituitary pars distalis (PD) of adult male viscachas during their annual reproductive cycle. In each period of this cycle (reproductive, gonadal regression and gonadal recovery periods), four pituitary glands were collected and processed for light microscopy. Apoptotic cells were detected by TUNEL and RE-immunoreactive (-ir) cells by immunohistochemistry. These cells were morphometrically quantified by image analysis. The percentage of cells per microscopic field were determined. The values were statistically analyzed and expressed as mean ± SEM. In all groups, TUNEL-positive nuclei were scarce in the medial region. However, they were abundant in the ventral region and at the rostral and caudal ends. In gonadal regression and gonadal recovery periods, the percentage of this nuclei were significantly higher than in the reproductive period (P < 0.01, P < 0.05). In addition, they were frequently located close to follicular structures and blood vessels. The immunostaining pattern for ERα was nuclear (ERαn) and cytoplasmic (ERαc). A cytoplasmic heterogeneous pattern predominated in all groups studied. The ER expression showed regional variations during the reproductive period. The REc-ir cells being higher in the medial region (P < 0.01) and less numerous at the rostral end (P < 0.01). The total percentage of REc-ir cells did not differ significantly among different groups, instead the total percentage of REn-ir cells was maximum in recovery period and minimum in gonadal regression period (P < 0.05). The regionalized expression of ER receptors and apoptotic cells could be related with the different PD cell populations and their variations throughout the reproductive cycle according to hormonal demand. Besides, these results demonstrated that the minimal expression of ERn was related with the maximal number of apoptotic cells in the gonadal regression period, suggesting that a decreased of ERn expression might stimulate the apoptotic processes in the pituitary during the annual reproductive cycle.