Reproductive efficiency represents a determining factor on the overall performance and profitability of livestock. Despite the significant improvement achieved by the Brazilian cattle industry following the use of hormonal protocols that improved the rate of inseminated animals, pregnancy rates remain low at first AI, indicating that a significant proportion of inseminated females failed to become pregnant. It has been established that a major factor affecting conception rates is early embryonic mortality, which encompasses a variety of aspects that may potentially interfere with the pre-implantation uterine environment. The premise of this proposal is that post-ovulatory variations in P4 concentrations regulate endometrial gene expression and, consequently, the qualitative and quantitative composition of the uterine secretions, thus influencing the receptivity of the uterus toward the early development of the conceptus. Among the numerous molecules of different biochemical nature that constitute the uterine secretions, we propose the study of organic cations that regulate cellular processes such as growth, development and differentiation called polyamines. Furthermore, we propose that polyamines are under regulation of the peri-ovulatory endocrine milieu. The main hypothesis of this proposal is that the peri-ovulatory endocrine environment regulates the polyamine transport and synthesis pathway in the endometrium during the first week of the estrous cycle in cattle. The aim of this proposal is to analyze the relative abundance of transcripts of the polyamine synthesis pathway, the expression of key proteins in this process as well as their cellular and tissue distribution in endometrial tissue, and compare these variables between two experimental groups with distinct post-ovulatory P4 concentrations. Experimental groups were obtained by means of hormonal manipulation of the pre-ovulatory follicle growth, which aimed to induce ovulation of larger follicles that resulted in larger corpora lutea and greater post-ovulatory P4 production (high P4 group; HP) or the opposite (low P4 group; LP). It is expected that molecules that compose the polyamine synthesis pathway will be differentially regulated between groups HP and LP. The potential regulation of this pathway by different peri-ovulatory endocrine environments will be critical for the definition of molecular signatures associated with higher or lower probability of gestational success. More specifically, it is expected that molecules identified as differentially regulated by the proposed experimental model will be investigated as potential prognostic or diagnostic markers of the gestational success.
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