Addition of Glutathione to an Extender for Frozen Equine Semen

The manipulation of equine semen during cryopreservation reduces sperm viability and fertility because of, among other factors, membrane lipid peroxidation that makes cells highly susceptible to free radicals and reactive oxygen species (ROS). The oxidative effect caused by the generation of ROS can be reduced by the addition of antioxidants to the seminal plasma or to the extenders used for freezing. The current study was performed to test the in vitro effect of exogenous glutathione added in five different concentrations (control, 2.5 mM, 5.0 mM, 7.5 mM, and 10 mM [treatments 1-5, respectively]) to the extender for 12 stallions. Analyzed parameters were sperm motility, viability, and acrosome and plasmatic membrane integrity. Total motility was higher in treatments 1 and 2 (P < .05); viability, progressive motility, and plasmatic membrane integrity were higher in treatment 2 (P < .001). As for acrosome membrane integrity, treatment 3 showed the best results (P < .05). The addition of 2.5 mM glutathione to the freezing extender preserves total motility and increases sperm viability, progressive motility, and plasmatic membrane integrity. Concentrations above 2.5 mM were deleterious to spermatozoa.