Acquisition of Luteolytic Capacity: Changes in Prostaglandin F2(alpha) Regulation of Steroid Hormone R(alpha) Regulation of Steroid Hormone Receptors and Estradiol Biosynthesis in Pig Corpora Lutea

The pig corpora lutea (CL) acquires luteolytic capacity at about Day 13 of the estrous cycle, after which luteolysis occurs in response to prostaglandin F2(alpha) ) treatment. We postulated that differences in transcription factors such as the steroid hormone receptors may be responsible for the differences in PGF2(alpha) on luteal expression of receptors for progesterone (nuclear and membrane progesterone receptor [PR]), estradiol (ER(alpha) and aromatase). Two experiments were conducted to examine the early (0.5 h, experiment I) and late (10 h, experiment II) effects of PGF2(alpha) decreased ER(alpha) in Day 17 CL but not Day 9 CL, with a dramatic increase in aromatase mRNA and luteal estradiol content. Nuclear PR was not affected by PGF2(alpha) , but was greater (176%) in Day 9 CL, while a putative membrane PR was greater (156%) in Day 17 than Day 9 CL. There were no detectable changes in glucocorticoid or androgen receptor mRNA. Thus, luteolytic capacity is associated with upregulation of estradiol biosynthesis, which in conjunction with increased ER(beta) expression and altered PR expression may promote luteolysis in the pig CL.