The effect of prostaglandins E₂ and F_2α on orexin system expression in the porcine uterus during the peri-implantation period

The aim of this study was to evaluate the effect of prostaglandins E₂ (PGE₂) and F_2α (PGF_2α) on orexins (OXA and OXB) secretion (ELISA), prepro-orexin (PPO) gene expression and the content of orexin receptors (OX1R, OX2R) mRNA (qPCR) and proteins (Western blot) in porcine endometrial and myometrial tissue slices during early pregnancy (days 10–28) and on days 10–11 of the oestrous cycle. On days 10–11 of pregnancy, prostaglandins (PGs) decreased the expression of the PPO gene and OXR gene and protein in the endometrium. On days 12– 13, PGs increased OXB secretion, PGE₂ enhanced OXA secretion, and PGF_2α suppressed PPO expression. On days 15–16, both PGs inhibited PPO expression and OXB secretion, and PGF_2α increased OXA release. On days 27–28, PGs decreased PPO mRNA and OX1R protein levels, PGE₂ decreased OX2R protein content, and PGF_2α decreased OXB secretion. On days 10-11 of the cycle PGs increased the expression of PPO mRNA and OX2R protein, whereas PGE₂ increased OX1R protein content. The effect of PGs on orexin system expression in the porcine myometrium was dependent on the animal physiological status and the concentrations of specific PGs. The study demonstrated that PGs exert regulatory effects on orexin system expression in the porcine uterus, which suggests that a local regulatory mechanism could be responsible for modulating uterine metabolism. The observed differences in PGs’ influence on orexin system expression could be attributed to changes in the sensitivity of the studied tissues, associated with the phase of the oestrous cycle, the stage of early pregnancy or PGs concentration.