Regulation of steady-state concentrations of messenger ribonucleic acid encoding prostaglandin F2α receptor in ovine corpus luteum

Abstract

To investigate the regulation of ovine luteal receptors for prostaglandin F2α (PGF2α), reverse transcription-polymerase chain reaction was used to produce a 284-bp partial cDNA that was 98% identical to that reported for the bovine PGF2α receptor (PGF2α-R). In situ hybridization localized mRNA for PGF2α-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 PGF2α-R. There was no difference in mean steady-state concentrations of mRNA encoding PGF2α-R among any of the days studied (range = 2.3 ± 0.3 to 3.5 ± 0.7 fmol PGF2α-R mRNA/μg 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 PGF2α, 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 PGF2α-R were decreased (p < 0.05) at 4, 12, and 24 h after injection of PGF2α. In experiment 3, ewes (midluteal phase) were administered saline, PGF2α, 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 PGF2α-R were decreased (p < 0.05) by PGF2α, and PMA treatment (4 and 12 h) but were increased (p < 0.05) at 24 h after LH treatment. In summary, 1) mRNA encoding PGF2α-R was localized to large luteal cells; 2) concentrations of mRNA encoding PGF2α-R did not vary during the estrous cycle; 3) treatment with PGF2α or PMA to activate protein kinase C decreased concentrations of PGF2α-R mRNA within 4 h of treatment; and 4) administration of LH increased concentrations of mRNA encoding PGF2α-R 24 h following injection.