Effects of oxygen concentration and antioxidants on the in vitro developmental ability, production of reactive oxygen species (ROS), and DNA fragmentation in porcine embryos

After in vitro maturation and fertilization of porcine oocytes, the fertilized embryos were cultured under 5 or 20% oxygen (O-2) for 7 days. In embryos cultured under 5% O-2 versus 20% O-2, development to the blastocyst stage was higher (36.3% versus 22.5%, P < 0.05); the hydrogen peroxide (H2O2) content as a reactive oxygen species was lower (92 pixels versus 111 pixels, P < 0.05); and fragmentation of DNA in 8- to 16-cell stage embryos (estimated by the comet assay) resulted in a shorter (P < 0.05) DNA tail (36 mu m versus 141 mu m). Antioxidants such as beta-mercaptoethanol (beta-ME) and Vitamin-E (Vit-E) suppressed oxidative damage in the embryos and improved their developmental ability. For embryos cultured under 20% O-2, there were the following differences (P < 0.05) between embryos exposed to 0 mu M versus 50 mu M beta-ME: 28% versus 57% developed to the blastocyst stage; 125 pixels versus 98 pixels per embryo in H2O2 content; and a DNA tail of 209 mu m versus 105 mu m. In addition, for embryos cultured under 20% O-2, there were also differences (P < 0.05) between those exposed to 0 mu M versus 50 mu M of Vit-E: 28% versus 40% rate of development to the blastocyst stage; 28.9 cells versus 35.9 cells in the expanded blastocyst; 122 pixels versus 95 pixels per embryo (H2O2 content); and 215 mu m versus 97 pm length of the DNA tail. Therefore, a low O-2 concentration during in vitro culture of porcine embryos decreased the H2O2 content and, as a consequence, reduced DNA fragmentation, and, thereby, improved developmental ability. (c) 2004 Elsevier Inc. All rights reserved.