REGULATION OF PROSTAGLANDIN-F2-ALPHA AND PROSTAGLANDIN-E RECEPTOR MESSENGER-RNA BY PROSTAGLANDIN-F2-ALPHA IN-OVINE CORPORA-LUTEA

Prostaglandins regulate many physiological functions, including reprod uction, by binding to specific plasma membrane receptors. In this stud y we evaluated the regulation of PGF(2 alpha) (FP) and. PGE (EP3 subty pe) receptors in ovine corpora lutea. In the first study, tissue distr ibution of FP and EP3 receptors was evaluated in 13 ovine tissues. FP receptor mRNA was present in 100-fold higher concentration in corpora lutea than in other tissues. Similarly, [H-3]PGF(2 alpha) binding was much greater in luteal plasma membranes than in membranes from other t issues. In contrast, EP3 receptor mRNA was more uniformly distributed, with high concentrations in adrenal medulla, inner myometrium, kidney medulla and heart. The distribution of [H-3]PGE(1) binding was genera lly similar to EP3 mRNA, with the exception that ovarian stroma, endom etrium and outer myometrium had high [H-3]PGE(1) binding but low conce ntrations of EP3 receptor mRNA. The second study evaluated the action of PGF(2 alpha) on luteal mRNA encoding FP and EP3 receptors. Ewes had PGF(2 alpha) or saline infused into the ovarian artery and corpora lu tea were removed at 0, 1, 4, 12 and 24 h. FP receptor mRNA decreased b y 50% at 12 and 24 h after infusion with PGF(2 alpha), whereas EP3 mRN A was unchanged. Treatment of large luteal cells with PGF(2 alpha), ph orbol didecanoate (protein kinase C activator), or ionomycin (calcium ionophore) decreased FP receptor mRNA after 24 h (P < 0.05). Glycerald ehyde 3-phosphate dehydrogenase mRNA was not changed by any treatment. These results show that EP3 receptors are expressed in many tissues a nd expression is not regulated by PGF(2 alpha). In contrast, FP recept ors are primarily expressed in corpora lutea and expression is inhibit ed by PGF(2 alpha).