Differential localization of placental extracellular superoxide dismutase as pregnancy progresses.

Abstract

The aim of this study was to determine placental localization and activity of extracellular superoxide dismutase, a nitric oxide modulator, during early gestation and to correlate these characteristics with fetal vascular development. First-trimester (n = 10) and second-trimester (n = 10) villi were obtained at elective pregnancy termination. Extracellular superoxide dismutase was localized by means of an immunoperoxidase method. Activity was measured by determining the inhibition of cytochrome c reduction at pH 10 and messenger ribonucleic acid expression by in situ hybridization. Extracellular superoxide dismutase was intracellular within villous trophoblasts until 17 weeks' gestation, when it relocated to the villous extracellular matrix. Activities were similar between first- and second-trimester villi. In situ hybridization confirmed extracellular superoxide dismutase messenger ribonucleic acid within trophoblasts throughout gestation. 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.