Elucidation of physiological roles of prostaglandin F_<2alpha> and its regulatory mechanism in the reproductive system

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It has been recognized for overe two decades that prostaglandin (PG) F_<2alpha> is of prime importance in initiating luteal regression in many species. We succeeded in the cloning of a cDNA encoding PGF_<2alpha> receptor. We recently demonstrated that its mRNA and receptor protein are abundantly expressed in corpus luteum of the ovary throughout the luteal phase of the estrous cycle and early and middle pregnancy, suggesting that PGF_<2alpha> may be involved in not only luteolysis but also luteal functions. This year we focused on the elucidation of the regulatory mechanisms of PGF_<2alpha> receptor mRNA expression and PG production, and obtained following results. 1) We revealed by RNA blot analyzes that serum progesterone level and expression of PGF_<2alpha> receptor mRNA in mouse ovary increased 1-16 h after administration of gonadotropins (PMSG,hCG,FSH) and cholera toxin, which activate adenylate cyclase and increase cAMP level. We also demonstrated that these agents induced the ex … More pression of PGF_<2alpha> receptor mRNA in luteal cells of preexisting mouse ovary. These results supports the above-mentioned notion that PGF_<2alpha> may be involved in not only luteolysis but also luteal funciton. 2) We succeeded in the cloning of PGF_<2alpha> receptor gene and showed that it spans over 30 kb and consists of 3 exons. The promoter region contains several binding motifs for transcription factors and was activated by TPA and forskolin. 3) In order to elucidate the regulatory mechanism of PG production, we first identified three urinary metabolites of PGF_<2alpha> in mice by gas chromatography and mass spectrometry. We examined the change of one of the metabolites and showed that the metabolite increased at the term of pregnancy, suggesting the involvement of PGF_<2alpha> in delivery. 4) We also demonstrated by Western blot analysis with anti-PGF synthase antisera that PGF synthase protein increased at the term of pregnancy and suggested that it may be responsible for the PGF_<2alpha> production. Less