Direct effects of oestradiol-17 beta and prostaglandin E-2 in protecting pig corpora lutea from a luteolytic dose of prostaglandin F-2 alpha.

Implants containing vehicle or oestradiol-17 beta (10 mg) were placed into pairs of corpora lutea (CL) with and without prostaglandin F-2 alpha (PGF-2 alpha) (100 micrograms) on Day 11 and CL were collected on Day 19, in cyclic gilts (Exp. 1). The results demonstrated that CL implanted with PGF-2 alpha with or without oestradiol-17 beta had a markedly lower (P less than 0.01) weight (mg) and progesterone concentration (ng/mg) than CL with vehicle-or oestradiol-17 beta-implanted or unimplanted CL, which were similar (149 and 7.2 vs. 304 and 49.6, respectively). In Exp. 2, CL implanted with vehicle, oestradiol-17 beta or PGE-2 remained fully functional until Day 19, whereas CL implanted with oestradiol-17 beta +/- PGF-2 alpha and PGE-2 + PGF-2 alpha exhibited lower (P less than 0.05) weight and progesterone concentrations; CL implanted with PGE-2 + PGF-2 alpha were heavier (P less than 0.05) and tended (P less than 0.10) to have greater progesterone concentrations than CL implanted with oestradiol-17 beta + PGF-2 alpha. In Exp. 3, a dose-dependent (P less than 0.05) effect of PGE-2 on preventing regression induced by PGF-2 alpha was observed on Day 19. These data demonstrate a direct effect of PGE-2, but not of oestradiol-17 beta in protecting the CL against luteolysis induced by PGF-2 alpha.