Effect of exogenous glutathione on the in vitro fertilization of bovine oocytes

Increased amounts of reactive oxygen species (ROS) during in vitro culture may cause cytotoxic damage to gametes and embryos. The main purpose of this study was to investigate the effect of glutathione (GSH), a ROS scavenger, supplemented during NF of bovine oocytes on embryo development using sperm atozoa from different bulls. The following experiments were performed: 1) m atured COCs were fertilized in the absence or presence of 1 mM GSH using se men from 4 bulls (Bulls A, B, C and D); 2) matured COCs were fertilized in the absence or presence of I mM GSH using semen from Bull C to examine sper m penetration, pronuclear formation and apposition; 3) COCs were fertilized with in the presence of either 0, 0.1, 1.0 or 10 mM GSH to examine the eff ect of GSH concentration using sperm from Bull C; 4) concentrations of GSH were measured both in the medium and in the oocytes during IVF Glutathione at 1mM in TVF medium affected the blastocyst formation, but not the cleavage rate. The effect on blastocyst formation was bull dependent: semen from Bull B and D had a negative, that from Bull C a positive and the one from Bull A no effect. The positive effect of Bull C semen increased t he rate of blastocyst formation from 20.1 to 27.3% in control and GSH treat ed samples, respectively. The increased rate was due to more zygotes reachi ng the 8-cell or greater stage by Day 4 after IVF. There was no change in t he fertilization or cleavage rates. The GSH was still stable after 18 h inc ubation in IVF medium, and there was a dose-dependent increase in the GSH c oncentration in the oocytes. It is concluded that the effect of GSH during IVF on the proportion of blastocysts is dependent on both bull and GSH conc entration. (C) 1999 by Elsevier Science Inc.