REGULATION OF STEADY-STATE CONCENTRATIONS OF MESSENGER-RIBONUCLEIC-ACID ENCODING PROSTAGLANDIN-F2-ALPHA RECEPTOR IN OVINE CORPUS-LUTEUM

To investigate the regulation of ovine luteal receptors for prostaglan din F-2 alpha (PGF(2 alpha)), reverse transcription-polymerase chain r eaction was used to produce a 284-bp partial cDNA that was 98% identic al to that reported for the bovine PGF(2 alpha) receptor (PGF(2 alpha) -R). In situ hybridization localized mRNA for PGF(2 alpha)-R specifica lly 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 estrou s cycle were analyzed for mRNA encoding PGF(2 alpha)-R. There was no d ifference in mean steady-state concentrations of mRNA encoding PGF(2 a lpha)-R among any of the days studied (range = 2.3 +/- 0.3 to 3.5 +/- 0.7 fmol PGF(2 alpha)-R mRNA/mu g poly[A](+) RNA as assessed by slot-b lot hybridization). In experiment 2, ewes on Day 11 or Day 12 of the e strous cycle were administered PGF(2 alpha), and corpora lutea were co llected 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 concentr ations of mRNA encoding PGF(2 alpha)-R were decreased (p < 0.05) at 4, 12, and 24 h after injection of PGF(2 alpha). In experiment 3, ewes ( midluteal phase) were administered saline, PGF(2 alpha), phorbol 12-my ristate 13-acetate (PMA), or LH via ovarian arterial injection, and lu teal tissue was collected 0, 4, 12, or 24 h later (n = 3-4 per treatme nt per time). Steady-state concentrations of mRNA encoding PGF(2 alpha )-R were decreased (p < 0.05) by PGF(2 alpha) and PMA treatment (4 and 12 h) but were increased (p < 0.05) at 24 h after LH treatment. In su mmary, 1) mRNA encoding PGF(2 alpha)-R was localized to large luteal c ells; 2) concentrations of mRNA encoding PGF(2 alpha)-R did not vary d uring the estrous cycle; 3) treatment with PGF(2 alpha) or PMA to acti vate protein kinase C decreased concentrations of PGF(2 alpha)-R mRNA within 4 h of treatment; and 4) administration of LH increased concent rations of mRNA encoding PGF(2 alpha)-R 24 h following injection.