Prostaglandin F(2α) induces distinct physiological responses in porcine corpora lutea after acquisition of luteolytic capacity

This study examines differences in intracellular responses to cloprostenol, a prostaglandin (PG)F(2α) analog, in porcine corpora lutea (CL) before (Day 9 of estrous cycle) and after (Day 17 of pseudopregnancy) acquisition of luteolytic capacity. Pigs on Day 9 or Day 17 were treated with saline or 500 μg cloprostenol, and CL were collected 10 h (experiment 1) or 0.5 h (experiment III) after treatment. Some CL were cut into small pieces and cultured to measure progesterone and PGF(2α) secretion. In experiment I, progesterone remained high and PGF(2α) low in luteal incubations from either Day 9 or Day 17 saline-treated pigs. Cloprostenol increased PGF(2α) production 465% and decreased progesterone production 87% only from Day 17 luteal tissue. Cloprostenol induced prostaglandin G/H synthase (PGHS)-2 mRNA (0.5 h) and protein (10 h) in both groups. In cell culture, cloprostenol or phorbol 12,13-didecanoate (PDD) (protein kinase C activator), induced PGHS-2 mRNA in luteal cells from both groups. However, acute cloprostenol treatment (10 min) decreased progesterone production and increased PGF(2α) production only from Day 17 luteal cells. Thus, PGF(2α) production is induced by cloprostenol in porcine CL with luteolytic capacity (Day 17) but not in CL without luteolytic capacity (Day 9). However, this change in PGF(2α) production is not explained by a difference in induction of PGHS-2 mRNA or protein.