Our research group used an hormonal protocol to obtain two groups of cows: the first one ovulated a large diameter follicle in which were associated high serum concentrations of estradiol during estrus and progesterone during diestrus (LF-LCL) and the other group ovulated a smaller diameter follicle and produced a smaller CL (SF-SCL). In addition, it was demonstrated that there is a discrepancy between protein concentrations of progesterone receptor (PGR) and estradiol receptor (ESR1) in the oviduct samples between those groups. The LF-LCL showed high protein concentrations of these receptors, yet low levels of mRNA when compared to the SF-SCL group, which showed an opposite profile. That is, somehow the hormonal concentrations change protein synthesis in a post-transcriptional way. Contiguously, researches demonstrate the influence of steroidal hormones on biosynthesis of enzymes to post-transcriptional factors synthesis, the microRNAs (miRNAs). The miRNAs are noncoding RNAs about 22 nucleotides that regulate mRNA translation, thus, change protein synthesis in several tissues. miRNAs biosynthesis is regulated by various ways, among them, the ovarian steroidal hormones pathway - estradiol and progesterone - which change miRNAs expression by ligand-dependent mechanisms related to their nuclear receptors (ESR and PGR). Inasmuch as: (1) it occurs biosynthesis regulation of miRNAs by steroidal hormones and (2) the experimental groups showed different protein expression according to the oviduct regions (ampulla and isthmus), our hypothesis is: there are differences in the genic expression of the enzymes involved in miRNAs biosynthesis between the groups LF-LCL and SF-SCL and between the regions, ampulla and isthmus.
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