In vivo intra-luteal implants of prostaglandin (PG) E1 or E2 (PGE1, PGE2) prevent luteolysis in cows. I. Luteal weight, circulating progesterone, mRNA for luteal luteinizing hormone (LH) receptor, and occupied and unoccupied luteal receptors for LH

Abstract Previously, it was reported that chronic intra-uterine infusion of PGE 1 or PGE 2 every four hours inhibited luteolysis in ewes. However, estradiol-17β or PGE 2 given intra-uterine every 8 h did not inhibit luteolysis in heifers, but infusion of estradiol + PGE 2 inhibited luteolysis in heifers. The objective of this experiment was to determine whether and how intra-luteal implants containing PGE 1 or PGE 2 prevent luteolysis in Angus or Brahman cows. On day-13 post-estrus, Angus cows received no intra-luteal implant and corpora lutea were retrieved or Angus and Brahman cows received intra-luteal silastic implants containing Vehicle, PGE 1 , or PGE 2 and corpora lutea were retrieved on day-19. Coccygeal blood was collected daily for analysis for progesterone. Breed did not influence the effect of PGE 1 or PGE 2 on luteal mRNA for LH receptors or unoccupied or occupied luteal LH receptors did not differ ( P  > 0.05) so the data were pooled. Luteal weights of Vehicle-treated Angus or Brahman cows from days-13–19 were lower ( P 1 or PGE 2 . Day-13 Angus luteal weights were heavier ( P P  > 0.05) to Angus cows on day-19 treated with intra-luteal implants containing PGE 1 or PGE 2 . Profiles of circulating progesterone in Angus or Brahman cows treated with intra-luteal implants containing PGE 1 or PGE 2 differed ( P P  > 0.05) between breeds or between cows treated with intra-luteal implants containing PGE 1 or PGE 2 . Intra-luteal implants containing PGE 1 or PGE 2 prevented ( P 1 or PGE 2 alone delays luteolysis regardless of breed. We also conclude that either PGE 1 or PGE 2 prevented luteolysis in cows by up-regulating expression of mRNA for LH receptors and by preventing loss of unoccupied and occupied LH receptors in luteal tissue.