Differential localization of placental extracellular superoxide dismutase as pregnancy progresses

OBJECTIVE: The aim of this study was to determine placental localization an d activity of extracellular superoxide dismutase, a nitric oxide modulator, during early gestation and to correlate these characteristics with fetal v ascular development. STUDY DESIGN: First-trimester (n = 10) and second-trimester (n = 10) villi were obtained at elective pregnancy termination. Extracellular superoxide d ismutase was localized by means of an immunoperoxidase method. Activity was measured by determining the inhibition of cytochrome c reduction at pH in and messenger ribonucleic acid expression by in situ hybridization. RESULTS: Extracellular superoxide dismutase was intracellular within villou s trophoblasts until 17 weeks' gestation, when it relocated to the villous extracellular matrix. Activities were similar between first- and second-tri mester villi. In situ hybridization confirmed extracellular superoxide dism utase messenger ribonucleic acid within trophoblasts throughout gestation. CONCLUSION: Extracellular superoxide dismutase is produced by trophoblasts early in pregnancy, but it remains intracellular until 17 weeks' gestation, which may be related to fetal vascular development.