During reproductive processes, prostaglandin (PG) E2 (PGE2) and PGF2α play important roles in which they often exert opposite effects. At the time of recognition of pregnancy in vivo, PGF2α is recognized as the luteolytic factor in ruminants and in most species including human, whereas PGE2 may exert a luteoprotective action. We have previously demonstrated that recombinant interferon-tau (rIFN-τ), the embryonic signal responsible for recognition of pregnancy in ruminants, stimulated in vitro the production of PGE2 and prostaglandin-endoperoxide synthase 2 (Ptgs2; also called cyclooxygenase-2) gene expression in both epithelial and stromal endometrial cells. Since PGE2 is the major prostaglandin produced by stromal cells, the effect on Ptgs2 could explain the increase in PGE2 output. At high concentrations, however, recombinant ovine (ro) IFN-τ acts on epithelial cells by changing the primary PG produced from PGF2α to PGE2. This change in the primary PG produced could be explained by a decrease in PGF synthase (PGFS) activity or an increase in PGE synthase activity, or by modulation of a putative PGE2–9-ketoreductase, which converts PGE2 into PGF2α. Therefore, we have investigated the regulation of the mRNAs for PGFS and PGE2-9-ketoreductase (9K-PGR), two enzymes that lead to the production of PGF2α. Others have described 9K-PGR activity in uterus, ovaries, kidney, and liver of different species and have established that this enzyme could possess both 9K-PGR and 20α-hydroxysteroid dehydrogenase (20α-HSD) activity. Some have concluded that 9K-PGR and 20α-HSD are identical enzymes. Using primers sequences chosen from homologous nucleotide sequences of published rabbit 20α-HSD/9K-PGR and rat 20α-HSD cDNAs, a 317-base pair (bp) fragment was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned, and sequenced. Homologies of 83% and 78% were found with rabbit and rat 20α-HSD, respectively. The presence of 20α-HSD/9K-PGR and prostaglandin F synthase (PGFS) mRNA expression was studied semiquantitatively in cultured epithelial cells using RT-PCR. Stimulation of cells with roIFN-t resulted in a biphasic response, an inhibition of PGF2α production at low dose (1 ng/ml) and a stimulation of PGE2 at high dose (10 μg/ml). The increase of PGE2 was accompanied by reduced 9K-PGR and PGFS mRNA gene expression. The effect of oxytocin (OT) was also studied, and the presence of OT had no effect on either 9K-PGR or PGFS gene expression. The 20α-HSD/9K-PGR transcript was also detected in other bovine tissues at different intensity (liver > kidney > testis > ovaries). We believe that the 9K-PGR and PGFS can be key enzymes in the regulation of specific PGs in the endometrium during the periimplantation period.
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1 January 2000
Detection and Regulation of the Messenger for a Putative Bovine Endometrial 9-Keto-Prostaglandin E2 Reductase: Effect of Oxytocin and Interferon-Tau
Eric Asselin,
Michel A. Fortier
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Biology of Reproduction
Vol. 62 • No. 1
January 2000
Vol. 62 • No. 1
January 2000