Post-implantation mouse embryos have the capability to generate and release reactive oxygen species

The capability of the mouse embryo to generate reactive oxygen species (ROS) was examined. Post-implantation embryos were carefully harvested on Day 8 of pregnancy and the production of ROS was quantified using luminol-sensitized chemiluminescence. The embryos were stimulated with either phorbol myristate acetate (PMA) or all-trans-retinal (retinal) and the reaction kinetics were followed over 10 min. ROS secretion was directly proportional to the number of embryos and was suppressed 56% by superoxide dismutase (SOD), 25% by mannitol and as little as 16% by catalase. Embryos deprived of trophoblast showed no light emission suggesting that the source of ROS generation is the trophoblast. Dihydronicotinamide adenine dinucleotide (NADH)-dependent oxidase activity in the plasma membrane of the trophoblast surface was demonstrated by cytochemical methods. The release of ROS into the extracellular medium during the phagocytic process has been related to the cytolytic effect exhibited by these molecules and, perhaps by this means, the trophoblast can play an active role in the phagocytosis of maternal cells during the process of embryo implantation.