Reproduction Abstracts

Progesterone (P₄) produced by the corpus luteum (CL) is required for the attainment of endometrial receptivity and further conceptus implantation. Induction of puberty with PMSG/hCG in gilts results in lower P₄ concentration in blood serum, that is accompanied by decreased endometrial expression of genes involved in conceptus-maternal interactions. Therefore, the present study aimed to determine the effect of P₄ supplementation in pregnant gilts on endometrial preparation for implantation. Prepubertal gilts were induced to ovulate with 750 IU PMSG / 500 IU hCG, and inseminated. On days 3 to 10 of pregnancy, gilts received i.m. injections of corn oil vehicle (n=4) or P₄ (50 mg/100 kg; n=4). Blood samples were collected each day beginning form day 1 of pregnancy to analyze the profile of P₄ concentration using RIA method. Animals were slaughtered on day 12 of gestation. Uterine luminal flushing (ULF) was examined for E₂, PGE₂ and IL6 concentrations with RIA/EIA. Uterine horns were weighted and endometrial expression of PTGS2, HOXA10, LIF, TGFβ1 and IL6 mRNA was determined using qPCR. P₄-treated gilts demonstrated greater concentrations of P₄ in peripheral blood serum on days 8 to 10 and had heavier uteri after slaughter (P<0.05). The concentration of E₂ in ULF increased, but PGE₂ decreased, after P₄ treatment (P<0.05). Neither IL6 content in ULF, nor endometrial IL6 mRNA expression differ between groups. Similarly, PTGS2, HOXA10 and TGFβ1 mRNA expression was not affected by P₄ injections. Summarizing, P₄ supplementation had no significant impact on the expression of markers of endometrial receptivity in the pig. Supported by NSC grant 2011/01/B/NZ9/07069.