Figure 3

Antioxidant mechanisms which protect the embryo against ROS excessive formation. Superoxide dismutase (SOD), glutathione peroxidase (GPX) and gamma-glutamylcysteine synthase (GCS) transcripts have been identified in the oocyte, embryo and oviduct. The non-enzymatic antioxidants hypotaurine, taurine and ascorbic acid have been found in follicular and tubal fluids. Metallothionein is synthesized by trophoblast cells, and acts by neutralizing ROS and releasing the cell survival factor Zn²⁺.