Progesterone receptor (PGR) for its action required connection of the coregulatory proteins, including coactivators and corepressors. The former group exhibits a histone acetyltransferase (HAT) activity, while the latter cooperates with histone deacetylase (HDAC). Regulations of the coregulators mRNA and protein and HAT and HDAC activity can have an indirect effect on the PGR function and thus progesterone (P4) action on target cells. The highest mRNA expression levels for the coactivators—histone acetyltransferase p300 (P300), cAMP response element-binding protein (CREB), and steroid receptor coactivator-1 (SRC-1)—and nuclear receptor corepressor-2 (NCOR-2) were found in the corpus luteum (CL) on days 6 to 16 of the estrous cycle. The CREB protein level was higher on days 2–10, whereas SRC-1 and NCOR-2 were higher on days 2–5. The activity of HAT and HDAC was higher on days 6–10 of the estrous cycle. All of the coregulators were localized in the nuclei of small and large luteal cells. The mRNA and protein expression levels of the examined coactivators and corepressor changed with the P4 level. Thus, P4 may regulate CL function via the expression of coregulators, which probably affects the activity of the PGR.
Myometrium tissue shows the expression of non-genomic membrane progesterone (P4) receptors, such as progesterone receptor membrane components (PGRMC) 1 and 2 and membrane progestin receptors (mPR) alpha (mPRα), beta (mPRβ), and gamma (mPRγ). Their variable expression in the bovine uterus during the estrous cycle and early pregnancy suggests that ovarian steroids and luteotropic and/or luteolytic factors may regulate the expression of these receptors in the myometrium. Therefore, this study aimed to examine the effect of P4, estradiol (E2), P4 with E2, prostaglandins (PG) E2 and F2α, oxytocin (OT), and tumor necrosis factor α (TNFα) on the gene expression of PGRMC1, PGRMC2, serpine-1 mRNA-binding protein (SERBP1), and mPRα, mPRβ, and mPRγ in bovine myometrial cells from days 6 to 10 and 11 to 16 of the estrous cycle. The PGE2 concentration and mRNA expression were determined by EIA and real-time PCR, respectively. The data indicated that P4 and E2 can affect the mRNA expression of all studied receptors and SERPB1. However, PGE2, OT, and TNFα could only modulate the expression of PGRMC1, PGRMC2, and SERPB1, respectively. Steroids/factors changed the expression of PGRMC and mPR genes depending on the dose, the stage of the estrous cycle, and the types of receptors. This suggests that the local hormonal milieu may influence the activity of these receptors and P4 action in myometrial cells during the estrous cycle.
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