PPAR ligand association with prostaglandin F2α and E2 synthesis in the pig corpus luteum—An in vitro study

The present study evaluated the involvement of PPARs in prostaglandin (PG) E2 and F2α production in the corpus luteum (CL) of pigs on days 10–12 and 14–16 of the estrous cycle or pregnancy. The tissue explants were incubated for 6 h in the presence of PPARα, PPARβ, PPARγ ligands. The concentration of PGs in the incubation media was determined by radioimmunoassay, while mRNA abundance of PG synthetases (PGES and PGFS) was analyzed by quantitative real-time PCR. It was found that L-165,045 and rosiglitazone stimulated PGES synthesis on days 10–12 of the estrous cycle, whereas all factors that were assessed did not affect PGE2 release. The PGFS mRNA abundance in the CL did not change in the presence of PPAR ligands during the assessment periods. However, PPARβ agonist inhibited PGF2α secretion on days 10–12 of the estrous cycle and on days 14–16 of pregnancy. Interestingly, PPAR antagonists, MK 886, GW 9662 or T0070907 decreased PGF2α release by the slices on days 10–12 of the estrous cycle. It is concluded that the CL has a different susceptibility (greatest during mid-luteal phase of the estrous cycle) to the PPAR ligands, which is related to the physiological status of animal. The inhibition of PGF2α release and augmentation of PGES mRNA concentration during mid-luteal phase of the estrous cycle might suggest luteotropic properties of PPAR ligands.