Cortisol effect and its receptor on bovine embryo production

Cortisol, the main glucocorticoid (GC) found in cattle, acts in several physiological processes, playing a key role at the beginning of pregnancy, because it regulates mechanisms involved in embryo implantation process in the endometrium (Michael; Papageorghiou, Human reproduction update, v 14, p. 497-517, 2008). The main mechanism of GC action is via its interaction with glucocorticoid receptor (GR), which has been identified in bovine embryos. According to this the objective of this study was to evaluate the GC mechanism of action in bovine IVP embryos. In experiment 1 we check if GR is important for early embryonic development. For this we silenced the translation of mRNA for GR, using the RNAi technique. IVP Bovine zygotes were injected with siRNA for GR 16 hours after IVF and were IVC for 8 days until blastocyst stage to analyze embryonic development and quantification of mRNA and protein for GR. Cleavage, blastocyst rates, relative quantitation of mRNA for GR and fluorescence were subjected to ANOVA (P 0.05) compared to control (67.1 ± 11 and 34.8 ± 9.8) according to cleavage and blastocyst rates, respectively. Because of greater morphological similarities between group of 0.1 µg/mL and the control, this concentration was chosen for analysis of the relative quantification of mRNA. Thus, in vitro produced embryos were incubated from the 1st day with or without 0.1 µg/mL of Cortisol, and on the 8th day were analyzed for gene expression, however there was no difference between groups for any of the transcripts analyzed. Therefore, we conclude that GR is important for the early embryonic development in cattle, however its action is not directly related to interaction with GC.