In vivo intra-luteal implants of prostaglandin (PG) E1 or E2 (PGE1, PGE2) prevent luteolysis in cows. II: mRNA for PGF2α, EP1, EP2, EP3 (A–D), EP3A, EP3B, EP3C, EP3D, and EP4 prostanoid receptors in luteal tissue

Previously, it was reported that chronic intra-uterine infusion of PGE1 or PGE2 every 4 h inhibited luteolysis in ewes by altering luteal mRNA for luteinizing hormone (LH) receptors and unoccupied and occupied luteal LH receptors. However, estradiol-17β or PGE2 given intra-uterine every 8 h did not inhibit luteolysis in cows, but infusion of estradiol + PGE2 inhibited luteolysis. In contrast, intra-luteal implants containing PGE1 or PGE2 in Angus or Brahman cows also inhibited the decline in circulating progesterone, mRNA for LH receptors, and loss of unoccupied and occupied receptors for LH to prevent luteolysis. The objective of this experiment was to determine how intra-luteal implants of PGE1 or PGE2 alter mRNA for prostanoid receptors and how this could influence luteolysis in Brahman or Angus cows. On day-13 Angus cows received no intra-luteal implant and corpora lutea were retrieved or Angus and Brahman cows received intra-luteal silastic implants containing Vehicle, PGE1, or PGE2 and corpora lutea were retrieved on day-19. Corpora lutea slices were analyzed for mRNA for prostanoid receptors (FP, EP1, EP2, EP3 (A–D), EP3A, EP3B, EP3C, EP3D, and EP4) by RT-PCR. Day-13 Angus cow luteal tissue served as pre-luteolytic controls. mRNA for FP receptors decreased in day-19 Vehicle controls compared to day-13 Vehicle controls regardless of breed. PGE1 and PGE2 up-regulated FP gene expression on day-19 compared to day-19 Vehicle controls regardless of breed. EP1 mRNA was not altered by any treatment. PGE1 and PGE2 down-regulated EP2 and EP4 mRNA compared to day-19 Vehicle controls regardless of breed. PGE1 or PGE2 up-regulated mRNA EP3B receptor subtype compared to day-19 Vehicle control cows regardless of breed. The similarities in relative gene expression profiles induced by PGE1 and PGE2 support their agonistic effects. We conclude that both PGE1 and PGE2 may prevent luteolysis by altering expression of mRNA for prostanoid receptors, which is correlated with changes in luteal mRNA for LH receptors reported previously in these same cows to prevent luteolysis.

► PGE1 or PGE2 intraluteal implants in cows prevent endogenous PGF2α decrease in mRNA for FP receptors.
► PGE1 or PGE2 intraluteal implants in cows do not affect mRNA for EP1 receptors.
► PGE1 or PGE2 intraluteal implants in cows decrease mRNA for EP2 and EP4 receptors.
► PGE1 or PGE2 intraluteal implants in cows increase mRNA EP3 (A–D), EP3A, EP3B, EP3C, or EP3D receptors.