enzyme expression in human fetal membranes Jennifer McIntosh, Eric Knudtson, Daniel Jackson, Kimberly Pecinosky, Dean Myers University of Oklahoma Health Sciences Center, Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Oklahoma City, OK OBJECTIVE: Progesterone is essential for maintaining pregnancy. In the fetal membranes, progesterone limits prostaglandin (PG) production during pregnancy. One potential mechanism for a local progesterone withdrawal in fetal membranes is a local progesterone metabolism to inactive metabolites via 20 reductases (aldoketo reductase (AKR) 1C1, C2 and C3) and 5 reductase (5 RDT). However, the expression of these enzymes in the fetal membranes has not been described. We hypothesized that members of the AKR1C and/or 5 RDT enzymes are expressed in one or more components of the fetal membranes. STUDY DESIGN: Placentas from were obtained under sterile conditions from consented subjects (n 3) undergoing term, scheduled cesarean delivery without having undergone labor. For each, the fetal membranes were then separated into the amnion, chorion and decidua and snap frozen at -80. The presence of messenger RNA (mRNA) for AKR1C1, AKR1C2, AKR1C3 and 5 RDT-type II was assessed by using reverse transcription PCR (RT-PCR) in triplicate followed by agarose gel electrophoresis with ethidium staining. Human cervical fibroblasts were used for comparison, as presence of all of these enzymes have previously been found and described. Cyclophilin was used as a housekeeping gene. RESULTS: AKR1C2, AKR1C3 as well as 5 RDT-II were expressed in amnion, chorion and decidua. AKR1C1 was not expressed in these tissues. The relative mRNA levels of AKR1C1, 2 and 5 RDT-type II were similar in amnion, chorion and decidua (Figure). CONCLUSION: AKR1C2, AKR1C3 and 5 RDT-II were expressed in the amnion, chorion and decidua of normal term pregnancies. This may imply that a local progesterone withdrawal facilitates removal of progesterone action in these tissues facilitating PG production at term. Future studies examining progesterone metabolism via these pathways and expression of these enzymes in non-laboring vs. laboring membranes may provide another avenue of local progesterone withdrawal in the final common parturition pathway.