Evaluation of ovarian glucocorticoid receptor α expression in cows gestated under heat stress conditions

HUBER E; NOTARO US; RECCE S; ORTEGA HH; REY F; SALVETTI NR; RODRÍGUEZ FM

Mar del Plata

Congreso; LXII Reunión anual de la Sociedad Argentina de Investigación Clínica (SAIC); 2018

Adverseambient conditions (temperature-humidity index (THI) exceeding the comfortthreshold (72) for 3 or more days) on dairy cows can affect reproduction notonly in a direct way, also in the progeny of animals that are gestated underthese stress conditions. In fact, the ovarian follicular reserve is establishedduring the first half of the fetal life (0-150 days) and many factors canaffect the future fertility of the offspring. Under stress situations, nervoussystem triggers a signaling cascade with a final secretion of glucocorticoids(GCs). It is known that GCs exert actions in the ovary, mainly through the GC receptorα (GRα). In this study, we evaluated gene expression of GRα in preovulatoryfollicles of cows gestated under heat stress in different stages of gestation,and epigenetic mechanisms that could regulate gene expression. Holstein cows(n=20) were divided in two groups: group 1 (cows gestated under heat stressbetween 0-150 days of gestation) and group 2 (cows gestated under heat stress between151 days-end of gestation). Higher levels of GRα were detected by Real Time PCRin follicular wall of preovulatory follicles of group 1 relative to group 2(p<0,05). For quantitative methylation analysis of the 5? UTR region of theGR gene, an AGENA?s MassARRAY platform was used. Similar levels of methylationwere found in both groups for every CpG analyzed. These data suggest that differentialexpression of GRα could be related to an altered ovarian response to GCs incows gestated under heat stress in first half of gestation. However, we couldnot confirm that this variation is due to differential methylation of the GRgene.