Ações da Prostaglandina F2α e Paraoxonase-1 na ovulação e prenhez de bovinos

Abstract

Ovulation is one of the most critical reproductive processes for the female involving a series of changes that affect the homeostatic balance. Inflammation, in turn, is defined as an adaptive response of a tissue to a harmful stimulus, which aims to reestablish homeostasis. In this sense, ovulation is considered an inflammatory process, as it involves a series of inflammatory mediators. Prostaglandin F2 (PGF) and paraoxonase-1 (PON1), which are important inflammatory mediators, have been shown to play important roles in the ovulation process and in the response of females to reproductive biotechniques. Thus, we aimed to identify the effects and possible mechanisms of action of PGF on ovulation and to evaluate potential associations between PON1 and fertility in cattle. In the first study we aimed to identify whether PGF would be able to stimulate the hypothalamic-pituitary axis in the periovulatory process. The results demonstrated that PGF does not induce any change in LH levels, suggesting that it does not act at the central level. Based on these results, another study was conducted to evaluate the local effect of PGF on ovulation. After intrafollicular injection of PGF, all cows ovulated within 24 hours, however, the same occurred in cows receiving placebo. In parallel, a study was conducted to evaluate the association among PON1 activity and ovulation rate, follicular growth and pregnancy by artificial insemination in Bos indicus beef cows. The results indicated that serum PON1 activity did not affect the evaluated parameters. Finally, another study was conducted to characterize single nucleotide polymorphisms (SNPs) in the promoter region of bovine PON1 gene and to correlate with serum PON1 activity in B. indicus cows. Eight SNPs were identified, however there was no association of any SNPs and PON1 enzymatic activity. Collectively, these studies contributed to the understanding of the relationships of inflammatory mediators with fertility parameters in bovine females. However, our results shown that there are still gaps to be filled in order to identify the mechanism of action of PGF in ovulation. In addition, it is suggested that although PON1 has already been shown to be a good fertility biomarker in B. taurus dairy cows, the same can not be applied for B. indicus dairy cows. Thus, complementary studies are necessary to clarify the mechanism of action of these two mediators.