Regulation of steady-state concentrations of messenger ribonucleic acid encoding prostaglandin F2 alpha receptor in ovine corpus luteum

Abstract

To investigate the regulation of ovine luteal receptors for prostaglandin F2 alpha (PGF2 alpha), reverse transcription-polymerase chain reaction was used to produce a 284-bp partial cDNA that was 98% identical to that reported for the bovine PGF2 alpha receptor (PGF2 alpha-R). In situ hybridization localized mRNA for PGF2 alpha-R specifically to large luteal cells. In experiment 1, pools of luteal tissue (n = 4/day) collected from ewes on Days 3, 6, 9, 12, and 15 of the estrous cycle were analyzed for mRNA encoding PGF2 alpha-R. There was no difference in mean steady-state concentrations of mRNA encoding PGF2 alpha-R among any of the days studied (range = 2.3 +/- 0.3 to 3.5 +/- 0.7 fmol PGF2 alpha-R mRNA/ microgram poly[A]+ RNA as assessed by slot-blot hybridization). In experiment 2, ewes on Day 11 or Day 12 of the estrous cycle were administered PGF2 alpha, and corpora lutea were collected 4, 12, or 24 h later (n = 4-5 per time point). Nontreated (n = 4) or saline-treated (n = 4) ewes served as controls. Luteal concentrations of mRNA encoding PGF2 alpha-R were decreased (p < 0.05) at 4, 12, and 24 h after injection of PGF2 alpha. In experiment 3, ewes (midluteal phase) were administered saline, PGF2 alpha, phorbol 12-myristate 13-acetate (PMA), or LH via ovarian arterial injection, and luteal tissue was collected 0, 4, 12, or 24 h later (n = 3-4 per treatment per time). Steady-state concentrations of mRNA encoding PGF2 alpha-R were decreased (p < 0.05) by PGF2 alpha and PMA treatment (4 and 12 h) but were increased (p < 0.05) at 24 h after LH treatment. In summary, 1) mRNA encoding PGF2 alpha-R was localized to large luteal cells; 2) concentrations of mRNA encoding PGF2 alpha-R did not vary during the estrous cycle; 3) treatment with PGF2 alpha or PMA to activate protein kinase C decreased concentrations of PGF2 alpha-R mRNA within 4 h of treatment; and 4) administration LH increased concentrations of mRNA encoding PGF2 alpha-R 24 h following injection.