Detection and regulation of the messenger for a putative bovine endometrial 9-keto-prostaglandin E-2 reductase: Effect of oxytocin and interferon-tau

During reproductive processes, prostaglandin (PG) E-2 (PGE(2)) and PCF2 alp ha 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, wherea s PGE(2) may exert a luteoprotective action. We have previously demonstrate d that recombinant interferon-tau (rIFN-tau), the embryonic signal responsi ble for recognition of pregnancy in ruminants, stimulated in vitro the prod uction of PGE(2) and prostaglandin-endoperoxide synthase 2 (Ptgs2; also cal led cyclooxygenase-2) gene expression in both epithelial and stromal endome trial cells. Since PGE, is the major prostaglandin produced by stromal cell s, 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 s ynthase (PGFS) activity or an increase in PGE synthase activity, or by modu lation 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 prod uction of PCF2 alpha. Others have described 9K-PGR activity in uterus, ovar ies, 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 ar e identical enzymes. Using primers sequences chosen from homologous nucleot ide 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 8 3% and 78% were found with rabbit and mt 20 alpha-HSD, respectively. The pr esence of 20 alpha-HSD/9K-PGR and prostaglandin F synthase (PGFS) mRNA expr ession 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 stimulatio n of PGE(2) at high dose (10 mu g/ml). The increase of PGE(2) was accompani ed 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-P GR or PGFS gene expression. The 20 alpha-HSD/9K-PGR transcript was also det ected in of her bovine tissues at different intensity (liver > kidney > tes tis > ovaries). We believe that the 9K-PGR and PGFS can be key enzymes in t he regulation of specific PGs in the endometrium during the periimplantatio n period.