Detection and regulation of the messenger for a putative bovine endometrial 9-keto-prostaglandin E2 reductase:: Effect of oxytocin and interferon-tau

During reproductive processes, prostaglandin (PG) E-2 (PGE(2)) and PCF2 alpha play important roles in which they often exert opposite effects. At the time of recognition of pregnancy in vivo, PGF(2 alpha) is recognized as the luteolytic factor in ruminants and in most species including human, whereas PGE(2) may exert a luteoprotective action. We have previously demonstrated that recombinant interferon-tau (rIFN-tau), the embryonic signal responsible for recognition of pregnancy in ruminants, stimulated in vitro the production of PGE(2) and prostaglandin-endoperoxide synthase 2 (Ptgs2; also called cyclooxygenase-2) gene expression in both epithelial and stromal endometrial cells. Since PGE, is the major prostaglandin produced by stromal cells, the effect on Ptgs2 could explain the increase in PGE(2) output. At high concentrations, however, recombinant ovine (ro) IFN-tau acts on epithelial cells by changing the primary PC produced from PCF2 alpha to PGE(2). This change in the primary PC 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 PGE(2)-9-ketoreductase, which converts PGE(2) into PGF(2 alpha). Therefore, we have investigated the regulation of the mRNAs for PGFS and PGE(2)-9-ketoreductase (9K-PGR), two enzymes that lead to the production of PCF2 alpha. 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 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) activity Some have concluded that 9K-PGR and 20 alpha-HSD are identical enzymes. Using primers sequences chosen from homologous nucleotide sequences of published rabbit 20 alpha-HSD/9K-PGR and rat 20 alpha-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 mt 20 alpha-HSD, respectively. The presence of 20 alpha-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 PCF2 alpha production at low dose (1 ng/ml) and a stimulation of PGE(2) at high dose (10 mu g/ml). The increase of PGE(2) was accompanied by reduced 9K-PGR and PGFS mRNA gene expression. The effect of oxytocin (OT) was also studied, anti the presence of OT had no effect on either 9K-PGR or PGFS gene expression. The 20 alpha-HSD/9K-PGR transcript was also detected in of her 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.